WO2000061322A1 - Piece en acier moule et produit en acier presentant une excellente aptitude au formage et procede de traitement d'acier en fusion prevu a cet effet, et procede de production associe - Google Patents

Piece en acier moule et produit en acier presentant une excellente aptitude au formage et procede de traitement d'acier en fusion prevu a cet effet, et procede de production associe Download PDF

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Publication number
WO2000061322A1
WO2000061322A1 PCT/JP2000/002296 JP0002296W WO0061322A1 WO 2000061322 A1 WO2000061322 A1 WO 2000061322A1 JP 0002296 W JP0002296 W JP 0002296W WO 0061322 A1 WO0061322 A1 WO 0061322A1
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WO
WIPO (PCT)
Prior art keywords
molten steel
piece
steel
solidification
mgo
Prior art date
Application number
PCT/JP2000/002296
Other languages
English (en)
Japanese (ja)
Inventor
Masafumi Zeze
Takashi Morohoshi
Ryusuke Miura
Shintaro Kusunoki
Yasuhiro Kinari
Masayuki Abe
Hiroshi Sugano
Kenichiro Miyamoto
Masaharu Oka
Yuji Koyama
Original Assignee
Nippon Steel Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP11101163A external-priority patent/JP2000288698A/ja
Priority claimed from JP11102184A external-priority patent/JP2000288692A/ja
Priority claimed from JP10237999A external-priority patent/JP2000288693A/ja
Priority claimed from JP11367399A external-priority patent/JP2000301306A/ja
Priority claimed from JP11133223A external-priority patent/JP2000328173A/ja
Priority claimed from JP11146443A external-priority patent/JP2000334559A/ja
Priority claimed from JP18011299A external-priority patent/JP4279947B2/ja
Priority claimed from JP11237031A external-priority patent/JP2001058242A/ja
Priority claimed from JP26727799A external-priority patent/JP2001089807A/ja
Priority claimed from JP2000066137A external-priority patent/JP2001252747A/ja
Priority claimed from JP2000086215A external-priority patent/JP4287974B2/ja
Priority to EP00915437A priority Critical patent/EP1099498A4/fr
Priority to CA002334352A priority patent/CA2334352C/fr
Priority to US09/719,206 priority patent/US6585799B1/en
Priority to AU36746/00A priority patent/AU753777B2/en
Application filed by Nippon Steel Corporation filed Critical Nippon Steel Corporation
Publication of WO2000061322A1 publication Critical patent/WO2000061322A1/fr
Priority to US10/222,362 priority patent/US6918969B2/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/108—Feeding additives, powders, or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys

Definitions

  • the present invention relates to a piece having a solidified structure having a uniform grain size, having few surface defects and internal defects, and having excellent processing characteristics and quality characteristics, and a steel material produced by processing the piece. About.
  • the present invention promotes the formation of solidification nuclei when producing molten steel after decarburization refining into a lump piece by using an ingot-making method or a continuous forging method, etc.
  • the present invention relates to a method for treating molten steel capable of improving the quality characteristics and the processing characteristics.
  • the present invention relates to a method for producing a chromium-containing molten steel having a fine solidified structure and having few surface defects and internal defects, and a seamless steel pipe manufactured using the method.
  • the slab, slab, bloom, billet, and thin-walled slabs have been manufactured by ingot casting using molten steel or continuous casting using a vibrating dies, belt casters, or strip casters. It is manufactured by forging into pieces etc. and cutting it into a predetermined size.
  • the strip After being heated in a heating furnace or the like, the strip is subjected to a process such as rough rolling or finish rolling to be a steel material such as a steel plate or a shaped steel.
  • pieces for seamless steel pipes are similarly manufactured by forming molten steel into blue billets by an ingot making method or a continuous forming method. After being heated in a heating furnace or the like, the strip is subjected to rough rolling to produce steel for pipe making. It is transported to the pipe making process. Then, this steel material is reheated, formed into a rectangular or circular shape, and then drilled using a plug to produce a seamless steel pipe.
  • This steel material and quality of this steel material are greatly affected by the processing conditions such as rolling and the solidified structure of the piece before processing.
  • the microstructure of the flakes is composed of a relatively fine chill crystal solidified by rapid cooling by the ⁇ type on the surface layer, a large columnar crystal formed inside it, and a central part, as shown in Fig. 7. It consists of formed equiaxed crystals, and in some cases, columnar crystals may reach the center.
  • such a steel pipe has surface defects such as dents and cracks due to the piece, or internal defects such as internal cracks, cavities, and center segregation. Remain.
  • the above defects are increased by forming and drilling, and cracks and cracks occur on the inner surface of the steel pipe. Defects such as scalp flaws occur. This leads to increased maintenance such as grinding, or reduced yield due to frequent debris.
  • the piece When coarse columnar crystals and large equiaxed crystals are present inside the piece, the piece has internal cracks caused by strain applied by bulging of the piece, straightening, etc. Internal defects such as center hole porosity (Zaku) due to solidification shrinkage and center segregation due to the flow of unsolidified molten steel at the end of solidification occur.
  • Zaku center hole porosity
  • the surface defects generated on the piece cause a decrease in yield due to an increase in maintenance such as grinding and frequent occurrence of debris.
  • this piece is used as it is for rough rolling, finish rolling, etc.
  • internal defects such as internal cracks, zags, and center segregation occur.
  • Residual steel may cause UST rejection, decrease in strength or deterioration of appearance, etc., causing problems such as increased care of steel and frequent debris.
  • Such surface defects and internal defects in the piece can be suppressed by improving the solidification structure of the piece.
  • the columnar surface of the piece is required. In addition to suppressing coarsening of the crystal, It is important to have a fine solidified structure.
  • the inclusion morphology in the molten steel is devised and the solidification process is controlled to make the solidification structure a fine equiaxed crystal structure.
  • Various attempts have been made to prevent the occurrence of surface defects and internal defects.
  • the superheat temperature from the actual molten steel temperature, With the liquid phase temperature of the molten steel subtracted to 40 ° C or less, it is pulled out while cooling in a mold, and the solidified piece is made to have an equiaxed crystallinity of 70% or more. There are ways to prevent the ringing that occurs.
  • the equiaxed crystals from the surface layer to the inside have any particle size, and ⁇ how the solidification structure of the pieces is uniform. About what to do So far it has not been clarified.
  • Japanese Patent Application Laid-Open No. 57-62804 discloses that, in order to eliminate internal defects such as center porosity in a piece, the piece is rolled down with unsolidified inside, and the vicinity of the center is reduced.
  • the vicinity of the center of the piece is crimped by reduction. A large rolling force is applied to the layer, which causes internal cracks and center segregation.
  • the rolling reduction is insufficient, internal defects such as center porosity remain, and due to this, when drilling in the pipe making process, internal defects such as cracks and dents occur and the quality of the steel pipe deteriorates. There are problems such as invitation.
  • the method of electromagnetically stirring molten steel in the above 2) includes, for example, as described in JP-A-49-52725 and JP-A-2-151354, a type II or a type III.
  • the molten steel in the solidification process is subjected to electromagnetic stirring to cut the tips of growing columnar crystals,
  • electromagnetic stirring to cut the tips of growing columnar crystals.
  • cut pieces of the crystal are used as solidification nuclei and the equiaxed crystallinity in the solidified structure of the piece is 60% or more to prevent rigging.
  • an electromagnetic stirrer is provided at a position of 1.5 to 3.0 m from the molten metal surface in the continuous casting mold, and a thrust of 60 mmHg is applied.
  • the unsolidified layer of the piece being manufactured is subjected to electromagnetic stirring to convert the solidified structure of the piece into a fine structure composed of equiaxed crystals, so that center segregation ⁇ the absence of internal defects such as center porosity
  • electromagnetic stirring to convert the solidified structure of the piece into a fine structure composed of equiaxed crystals, so that center segregation ⁇ the absence of internal defects such as center porosity
  • a wire containing oxides of W, Mo, etc. is added to molten steel, and a stirring flow by electromagnetic stirring is applied to the position where the wire is melted to make the entire piece a solidified structure composed of equiaxed crystals
  • a method is described.
  • the dissolution of the additive in the wire is unstable, and there is a case where a residual remains. If residual melt occurs, this residual melt causes product defects.
  • even if all the additives in the wire are dissolved it is very difficult to disperse the additives uniformly from the surface layer to the inside of the piece, and as a result, the size of the solidified structure becomes uneven. Not preferred.
  • Japanese Patent Application Laid-Open No. 63-140061 discloses a method of adding fine particles such as TiN at the time of manufacturing. However, when this method is carried out, the same method as in Japanese Patent Application Laid-Open No. 53-90129 is used. Defects develop.
  • TiN is formed in molten stainless steel and the solidified structure is equiaxed. It is generally known to crystallize (eg, iron and steel, 1974-79). However, in order to obtain a sufficient equiaxed crystallization effect by the generation of TiN, As described in “Steel,” it is necessary to increase the Ti concentration in molten steel to 0.15% by weight or more.
  • the amount of expensive Ti alloy added must be increased, which ultimately increases the manufacturing cost and further increases the manufacturing cost.
  • problems such as nozzle throttling due to the coarse TIN and scoring flaws on the product plate occur.
  • the composition of steel is restricted by the relationship with the amount of TiN to be added, so that applicable steel types are limited.
  • Mg has a boiling point of about 1107 ° C, which is lower than the melting temperature, and has almost no solubility in the molten steel.Thus, even if metallic Mg is added to or added to molten steel, most of it escapes as steam. I will. Therefore, in general, even if it is added by a usual method, the Mg yield becomes very low, so it is necessary to consider the method of adding Mg.
  • the present inventor has found that while conducting research on the addition of Mg, the yield of Mg and the composition of the oxide generated after the addition of Mg are affected not only by the molten steel component but also by the slag component. In other words, it has been found that it is difficult to generate inclusions having a composition that effectively acts as solidification nuclei in molten steel simply by adding Mg to the molten steel.
  • Japanese Unexamined 7 -486 16 discloses a slag covering the molten steel surface in a container of the ladle or the like, a MgO 3 to 1 5% by weight, FeO, Fe 2 0 3 and MnO to 5 wt% or less the Cat) ⁇ S i 0 2 ⁇ a 1 leave 2 0 3 based slag, by adding Mg alloy through the slag, increasing the Mg yield in molten steel, moreover, fine MgO, and a method of improving the quality of steel to form oxides of MgO 'a l 2 0 3 is described.
  • JP-7 -48 616 JP method since covering the CaO ⁇ Si0 2 ⁇ A 1 2 0 3 based slag on the surface of the molten steel, it is possible to improve the yield by suppressing the evaporation of Mg It has the advantage that.
  • FeO in the slag covering the molten steel the total amount of Fe 2 0 3 and MnO only defined as 5 wt% or less, but does not specify Si0 2 content. Then, when the high content of Si0 2 in the slag, when the addition of metallic Mg and Mg alloy, Mg is to reaction with Si0 2 contained in the slag, reduction in Mg yield in molten steel I do.
  • a 1 2 0 3 based oxide Since A 1 2 0 3 based oxide, the degree of the action of the solidified core is small, the solidification structure of ⁇ piece is coarse, the interior or surface of the ⁇ , cracks and medium Kokorohen ⁇ , center porosity, etc. Defects occur, leading to a decrease in one-sided yield.
  • the steel material processed from this piece also has problems such as the occurrence of surface defects and internal defects caused by a coarse solidified structure, leading to a decrease in yield and quality.
  • JP-A-10-102131 and JP-A-10-296409 disclose that 0.001 to 0.015% by weight of Mg is contained in molten steel to form a fine and highly dispersible oxide.
  • a method has been proposed to improve the coagulation structure of a piece by distributing it over the entire piece.
  • 50 oxides are uniformly distributed from the surface layer of a piece to the inside. Since it is distributed at a high density of 2 mm2 or more, cracks and dents caused by oxides, etc. on the piece, the piece in the middle of processing, or the steel material obtained by processing the piece Defects may occur. In such a case, care such as surface grinding is required, and the yield of products is reduced because the steel material is scrapped.
  • oxides are exposed on the surface of the steel material or oxides are present in the vicinity of the surface layer, the oxides (MgO-containing oxides) ) Is eluted and the corrosion resistance of steel materials is reduced.
  • the present inventor conducted various experiments to find the optimum conditions for equiaxed crystallization by adding Mg to molten steel, and as a result, even if the same molten steel composition and Z or the same slag composition were obtained.
  • deoxidizing element such as A1 and Mg added greatly affects the equiaxed crystallization effect.
  • the present invention has been made in view of such circumstances, and makes the solidified structure a fine and uniform solidified structure, suppresses the occurrence of surface defects and internal defects such as cracks, center porosity, and center segregation, and has processing characteristics. Another object is to provide a piece having excellent quality characteristics.
  • Another object of the present invention is to provide a steel material obtained by processing this piece, which is free from surface defects and internal defects, and has excellent processing characteristics and Z or quality characteristics.
  • the present invention promotes the production of a high-melting MgO-containing oxide in molten steel, and acts as a solidification nucleus to make the solidified structure of a piece finer.
  • the purpose of the present invention is to provide a processing method.
  • the present invention provides a fine solidification structure of a piece, suppresses the occurrence of surface defects such as cracks and segregation and internal defects, and generates a steel piece when the piece is processed into a steel material. Less defects and quality such as corrosion resistance It is an object of the present invention to provide a continuous manufacturing method capable of manufacturing a piece having excellent characteristics.
  • An object of the present invention is to provide a method of manufacturing a piece of chromium-containing steel that can reduce defects generated in a steel pipe and improve product yield and the like, and a steel pipe manufactured from the piece.
  • piece A The piece (hereinafter referred to as “piece A”) of the present invention meeting the above object is characterized in that 60% or more of the entire cross section of the fabricated piece is an equiaxed crystal satisfying the following formula.
  • D is the diameter (mm) of the equiaxed crystal as a structure having the same crystal orientation
  • X is the distance (mm) from the surface of the piece.
  • the width of columnar crystals remaining on the surface layer of the ⁇ ⁇ piece is reduced, and the segregation at the mouth due to the solid-liquid distribution of the molten steel component during solidification is suppressed.
  • piece A having a solidified structure that satisfies the above equation has uniform deformation and high processing characteristics when subjected to rolling or other processing. Therefore, in the processed steel, surface defects and internal defects are reduced. Generation is suppressed.
  • the equiaxed crystal can occupy the entire cross section of the piece.
  • the entire cross section of the piece is made into a uniform and fine solidification structure without columnar crystals, and the micro segregation in the surface layer and inside of the piece is made smaller, the solidification process
  • the cracking resistance caused by the strain and stress of the steel can be further enhanced.
  • surface defects and internal defects can be further prevented from occurring in the piece, and the uniformity of deformation during the processing from the surface layer to the inside of the piece increases, thereby improving the processing characteristics.
  • Piece Another piece (hereinafter referred to as “piece”) having excellent processing characteristics of the present invention meeting the above-mentioned object.
  • the piece B 60% or more of the cross section in the thickness direction of the piece can be made equiaxed.
  • the solidified structure of the piece can be made a solidified structure in which the growth of columnar crystals is suppressed.
  • grain boundary segregation in the surface layer and inside of the piece is further suppressed, cracking resistance due to distortion and stress in the solidification process is increased, and the occurrence of surface defects and internal defects in the piece is suppressed, and This improves the isotropy of the deformation behavior (extending in the width and length directions due to the reduction) and the processing characteristics. That is, it is possible to prevent the occurrence of surface defects such as cracks, scabs, and wrinkles due to non-uniform processing deformation in the steel material.
  • the entire cross section in the thickness direction of the piece can be made equiaxed.
  • the piece (hereinafter referred to as “piece”) having excellent quality characteristics and processing characteristics according to the present invention meeting the above-mentioned object has a degree of lattice mismatch with ferrite of ⁇ 5 formed during solidification of molten steel of 6%. It is characterized by containing 100 or more Zcm 2 of the following inclusions.
  • Inclusions with a small degree of lattice mismatch with 5-Funylite efficiently act as inoculation nuclei that generate a large number of coagulation nuclei. If a large number of solidification nuclei are formed, the solidification structure becomes fine, and as a result, microsegregation in the surface layer and inside of the piece is suppressed, and crack resistance against uneven cooling and shrinkage strain is improved. I do. Further, the solidification nucleus performs a pinning action after solidification (suppresses the growth of crystal grains immediately after solidification), thereby suppressing the coarsening of the solidified tissue and obtaining a more stable fine solidified structure.
  • the piece having such a solidified structure easily deforms in the reduced direction when subjected to processing such as rolling. That is, this piece has a very high addition characteristic.
  • the size of the inclusion was 10 m or less. Of inclusions of 100 or more cm 2 can be contained.
  • a piece having such a solidified structure has high workability when performing processing such as rolling, and does not generate surface defects such as dents, surface cracks, and wrinkles, and internal defects in the steel material.
  • the size of the inclusions is larger than 10 m, it will act as a solidification nucleus when the molten steel solidifies, but it will easily cause sliver and sliver flaws.
  • the piece C may be of a steel type having a solidification primary crystal of 5 flies.
  • a piece according to the present invention having excellent quality characteristics according to the present invention (hereinafter referred to as “piece D”) is manufactured by adding a metal or a metal compound for forming a solidification nucleus during solidification of molten steel to molten steel.
  • the number of metal compounds having a size of 10 im or less contained inside the surface layer is 1.3 or less with respect to the number of metal compounds having a size of 10 m or less contained in the surface portion of the piece. It is characterized by being twice or more.
  • piece D of the metal compound formed by adding a metal to molten steel or a metal compound having a size of 10 / m or less among metal compounds added directly to molten steel, the surface layer of the piece It is contained more inside the pieces.
  • This metal compound acts as a solidification nucleus when the molten steel solidifies, reducing the equiaxed crystal size of the solidified structure and, as a result, suppressing grain boundary segregation. You.
  • this metal compound forms a pinning action and suppresses coarsening of equiaxed crystals after solidification.
  • the number of metal compounds in the surface layer is smaller than the number of metal compounds in the inside, so that when the piece is subjected to processing such as rolling, it is caused by inclusions.
  • the generated surface defects are reduced, and the quality characteristics such as corrosion resistance and the workability are improved.
  • the surface layer portion in piece D means a range of more than 10% from the surface layer to 25% from the surface layer. Outside of this range, the surface layer becomes too thin and the interior with a large amount of metal compounds becomes closer to the surface, or the number of metal compounds inside increases, and the surface layer cannot be formed into a fine solidified structure. Defects due to the metal compound are likely to occur when applying the heat treatment to the metal.
  • the metal compound contained in the molten steel is formed at the time of solidification of the molten steel (the degree of lattice mismatch with the 5-flight may be 6% or less.
  • piece D is made of ferritic stainless steel piece. it can.
  • the solid structure can be easily made into fine equiaxed crystals.
  • the piece of the present invention can contain an MgO-containing oxide formed by adding Mg or a Mg alloy to molten steel.
  • the MgO-containing oxide By containing the MgO-containing oxide, it is possible to suppress the agglomeration of the oxide in the molten steel, increase the dispersibility of the oxide, and increase the number of oxides acting as solidification nuclei. As a result, the solidified structure of the piece becomes a more stable and fine solidified structure.
  • the above piece of the present invention is made into a steel material after being heated, for example, heated to 1100 to 1350 ° C., and then subjected to processing such as rolling to obtain a steel material. Because it has a high resistance to cracking during processing such as rolling, it prevents deformation from being concentrated on specific crystal grains during processing, and uniform deformation of crystal grains (isotropic deformation behavior) ) Is obtained.
  • the steel piece of the present invention is uniformly deformed in the width and length directions when it is rolled down, so that the steel material of the present invention obtained by processing the steel piece has a flaw generated on the steel material.
  • the occurrence of surface defects such as cracks and internal defects such as center opening and center segregation are extremely small.
  • the steel material of the present invention has few surface defects and internal defects caused by inclusions, and has good quality characteristics such as corrosion resistance.
  • processing method of the present invention a method of processing molten steel required to produce the above-mentioned piece of the present invention.
  • processing method I is to reduce the total Ca content in molten steel refined in a refining furnace to 0.0001% by mass or less, and then to the molten steel. It is characterized in that a predetermined amount of Mg is added.
  • This treatment method I can be in the molten steel, to suppress the formation of calcium-aluminum Ne Ichito (low-melting inclusions such as 1 2 CaO ⁇ 7 A 1 2 0 3). Formation of ternary composite oxide of MgO - result, CaO _ A l 2 0 3 that Mg oxide (MgO) is formed to join the calcium 'aluminum Natick DOO The by preventing, refractory oxides such as MgO and MgO * Al 2 0 3 as a coagulating core can and forming child.
  • the total Ca amount is the total amount of Ca present in the molten steel and the Ca content of Ca-containing compounds such as CaO, and the content specified by the treatment method I is the amount of Ca contained in the molten steel. This is the content when it is not contained at all, or when it is contained at 0.0010% by mass or less.
  • the molten steel may not contain a calcium-aluminate composite oxide.
  • the oxide in the molten steel when (MgO) is present typically, ternary complex oxide of CaO-A1 2 0 3 -MgO formed by calcium 'aluminum Natick preparative oxide (MgO) it is possible to prevent the formation stably, resulting refractory oxide 2 0 3 or the like MgO and MgO 'Al in the molten steel (hereinafter, the this as "Mg0-containing oxide”.) more the It can be surely formed, and the solidification structure of the piece can be made finer to prevent surface defects and inner surface defects from occurring in the piece.
  • Mg0-containing oxide ternary complex oxide of CaO-A1 2 0 3 -MgO formed by calcium 'aluminum Natick preparative oxide
  • the amount of Mg added to the molten steel is preferably 0.0010 to 0.10 mass%.
  • the amount of Mg is less than 0.0010% by mass, the number of solidification nuclei due to the MgO-containing oxide in the molten steel decreases, and the solidification structure cannot be refined.
  • the added amount of Mg exceeds 0.10% by mass, the effect of refining the solidified structure is saturated, the added Mg and Mg alloy are wasted, and oxides including MgO and oxides containing MgO are added. Defects may occur due to the increase in
  • the piece of the present invention manufactured by pouring molten steel treated by the treatment method I of the present invention into a mold and cooling the molten steel has a fine solidified structure by fine MgO and oxides containing MgO or MgO. And ⁇ surface defects such as cracks and dents generated on the surface of the piece, internal cracks, and internal defects such as center porosity (Zaku) and center segregation are suppressed. And this When steel pieces are manufactured by rolling or other processing on the steel pieces, surface defects and internal defects are prevented from occurring in the steel materials, and care and debris are eliminated, improving product yield and material quality I do.
  • treatment method ⁇ Another treatment method of the present invention is to add a predetermined amount of an A1-containing alloy to molten steel before adding a predetermined amount of Mg to the molten steel, and perform a deoxidation treatment. It is characterized by performing.
  • the processing method ⁇ is added previously to the A1-containing alloy, and the A1-containing alloy, oxygen in the molten steel, is reacted with MnO, Si0 2, FeO, etc. to produce a A 1 2 0 3, thereafter, by adding a predetermined amount of Mg, the surface of the AI 2 0 3, MgO was produced by the oxidation of Mg, or a shall form a MgO * Al 2 0 3.
  • MgO present on the surface of the A 1 2 0 3, or, MgO 'Al 2 0 3 is a solidified primary crystal ⁇ 5 off Juraj bets and the lattice mismatch is less than 6% der Runode, molten steel solidification In doing so, it acts as a coagulation nucleus.
  • the solidified structure is refined, and the occurrence of surface defects such as cracks, internal segregation such as center segregation, and center porosity is suppressed, and further, deterioration in workability and corrosion resistance is also suppressed.
  • A1 containing alloy means a metal containing A1 such as metal A1 or Fe-A1 alloy, and Mg to be added is metallic Mg, Mg-containing alloy such as Fe-Si-Mg alloy, Ni-Mg alloy, etc.
  • a predetermined amount of the Ti-containing alloy may be added to perform the deoxidation treatment.
  • the Ti-containing alloy By the addition of the Ti-containing alloy, is dissolved the Ti in the molten steel, the partially is generated as ⁇ and allowed action as a solidification nucleus, moreover, of A 1 2 0 3 produced by deoxidation on the surface, to form a MgO or MgO ⁇ a 1 2 0 3, together, can act as a solidification nucleus.
  • the Ti-containing alloy means a metal containing Ti, such as metallic Ti or Fe_Ti alloy.
  • the amount of Mg added is preferably set to 0.0005 to 0.010% by mass.
  • Mg in the range, MgO in A1 2 0 3 of the surface generated by deoxidation, or a MgO ⁇ A 1 2 0 3 can be sufficiently formed.
  • the Mg 0 or MgO ⁇ A 1 2 0 3 is when the molten steel solidifies, and the solidified core thoroughly for work, the solidification structure finer.
  • the added amount of Mg is less than 0.0005% by mass, the number of oxides having a surface with lattice mismatch of 6% or less with ⁇ 5 lights is insufficient, and the solidified structure cannot be refined. .
  • the added amount of Mg exceeds 0.010% by mass, the effect of the oxide to refine the solidified structure becomes saturated, and the cost required for adding Mg increases.
  • the molten steel can be a molten stainless steel.
  • the solidification structure of the monolithic stainless steel whose solidification structure is likely to be coarsened can be refined, and as a result, cracks and dents generated on the surface of the piece, internal cracks, Center porosity and center segregation can be suppressed.
  • oxides such as slag and deoxidation products contained in the molten steel and oxides generated when Mg is added to the molten steel include the following (1) and It is more preferable to add Mg so as to satisfy the expression (2).
  • k mol% of the oxide.
  • the addition of Mg, 5 full Erai preparative lattice mismatch is less than or equal to 6% of an oxide which acts effectively as a solidification nucleus CaO * A 1 2 0 3 ⁇ MgO,
  • Mg can also be applied to molten steel of ferritic stainless steel. It is possible to suppress internal cracks, center segregation, center porosity, etc., which occur in the piece. Further, in the steel material obtained by processing the piece, it is possible to prevent the occurrence of pitting and edge seam flaws caused by a coarse solidified structure.
  • processing method m Another processing method of the present invention is to add a predetermined amount of Mg to molten steel having a Ti concentration and an N concentration satisfying a solubility product in which TiN is crystallized at a temperature higher than a liquidus temperature of the molten steel. It is characterized by doing.
  • TIN During high temperature without crystallisation, good MgO or MgO dispersible 'Al 2 0 3 of MgO-containing oxides generated, as the molten steel temperature drops, the MgO content' oxide The TiN crystallizes on the material and disperses in the molten steel, which acts as solidification nuclei to refine the solidification structure of the piece.
  • the addition of Mg is performed by introducing a Mg-containing alloy such as metallic Mg or a Fe—SI—Mg alloy or a Ni—Mg alloy.
  • the Ti concentration [% Ti] and the N concentration [% N] preferably satisfy the following equations.
  • [% Ti] is the Ti mass% in the molten steel
  • (% N] is the N mass% in the molten steel
  • (% Cr) is the Cr mass% in the molten steel.
  • the concentration of Ti and N contained in the molten steel is maintained in a predetermined range, and a predetermined amount of Mg is added. It can be stably dispersed in molten steel accompanying oxides.
  • This TiN acts as a solidification nucleus when the molten steel solidifies, making the solidified structure of the piece finer.
  • the treatment method ⁇ of the present invention exerts the effect of refining the solidification structure even on Cr-containing frit-based stainless steel whose solidification structure is likely to become coarse, and ⁇ surface defects and internal defects occur in the single-piece steel material. You can prevent it from being ⁇ £>.
  • the treatment method of the present invention is particularly suitable for the production of a molten stainless steel containing 10 to 23% by mass of Cr.
  • the Cr content is less than 10% by mass, the corrosion resistance of the steel material is reduced, and the desired refining effect cannot be obtained.
  • the Cr content exceeds 23% by mass, the corrosion resistance of the steel material will not be improved even if Cr ferromagnetic iron is added, and the addition amount of ferromagnetic iron will increase, thus increasing the production cost.
  • processing method IV Another processing method of the present invention is characterized in that the slag covering the molten steel contains 1 to 30% by mass of an oxide reduced by Mg. .
  • the ratio (yield) of Mg added to molten steel to produce oxides containing MgO and MgO is high.
  • fine MgO or an oxide containing MgO (hereinafter referred to as “MgO-containing oxide”) can be dispersed in the molten steel.
  • the MgO or MgO-containing oxide acts as a solidification nucleus, and the solidified structure of the piece is refined. As a result, cracks and dents generated on the surface of the piece, cracks generated inside, center segregation, center porosity, etc. can be suppressed. By improving the yield of the piece, the quality of the steel material obtained by subjecting the piece to processing such as rolling can be improved.
  • the oxide of the slag refers to FeO, Fe 2 0 3, MnO , Si0 2 1 or two or more.
  • Et al is, in the processing method W of the present invention, arbitrary preferred to the A1 2 0 3 contained in molten steel from 0.005 to 0.10 wt%.
  • the high A 1 2 0 3 melting point can be a complex oxide such as MgO * Al 2 0 3, moreover, by utilizing the dispersibility of MgO, uniform the composite oxide in the molten steel The proportion of the MgO-containing oxide that disperses and acts as a solidification nucleus can be increased.
  • treatment method V Another treatment method of the present invention is to reduce the activity of CaO in the slag covering the molten steel to 0.3 or less before adding a predetermined amount of Mg to the molten steel.
  • Mg added to the molten steel produces finely MgO with excellent lattice matching with 5-ferrite and MgO-containing oxides with high melting points, which are dispersed in the molten steel. Can be done.
  • the MgO and the MgO-containing oxide act as solidification nuclei, so that the solidified structure of the piece becomes fine.
  • the basicity of the slag is 10 or less.
  • the CaO The activity can be suppressed stably, and the MgO-containing oxide is prevented from becoming an oxide having a low melting point or an oxide having a degree of lattice mismatch with the ⁇ 5 filler exceeding 6%. be able to.
  • processing method V of the present invention can be suitably applied to molten steel of a flint-based stainless steel.
  • the treatment method V of the present invention is applied to the treatment of molten steel of ferritic stainless steel, when the molten steel solidifies, the solidified structure that easily becomes coarse can be made fine, and the flakes and the steel material obtained by processing the same And other surface and internal defects occurring on the surface can be prevented.
  • the above-mentioned piece of the present invention can be manufactured by continuous casting.
  • molten steel containing MgO or an oxide containing MgO is poured into a mold, and the molten steel is stirred by an electromagnetic stirrer. It is characterized in that it is made while producing.
  • a highly dispersible MgO and / or Z or MgO-containing oxide is formed in molten steel, and the oxide promotes the formation of solidification nuclei and the pinning action (the growth of the microstructure immediately after solidification is suppressed). By doing so, the solidified structure of the piece can be refined.
  • the oxides present on the surface layer of the piece can be reduced by the stirring by the electromagnetic stirring device, and in the piece steel, defects such as dents and cracks caused by the oxide can be reduced. Prevention and increase corrosion resistance.
  • the electromagnetic stirrer is installed in a range from the meniscus in the mold to a position 2.5 m downstream.
  • the solidified structure of the surface layer is made fine while washing out the oxides trapped in the initially solidified surface layer, and a large amount of MgO and / or MgO-containing oxide is contained inside the piece. ,
  • the solid structure can be made into a finer solidified structure. As a result, in the single-piece steel material, defects such as hair flaws and cracks generated by the oxide can be prevented, and the corrosion resistance can be improved.
  • the flow rate of the stirring flow applied to the molten steel by the electromagnetic stirring device is set to l O cmZ seconds or more, whereby the oxidation captured by the solidified shell of the piece is preferably performed. Objects can be removed while being washed by the flow of molten steel.
  • the electromagnetic stirrer is preferably installed so as to impart a horizontal swirling flow to the molten metal surface in the mold.
  • the agitated flow swirling in the horizontal direction enables the oxide trapped in the surface layer of the piece to be efficiently removed while washing, thereby allowing many fine oxides to exist inside the piece.
  • the continuous manufacturing method of the present invention can be suitably applied to a case where a piece is manufactured from molten steel of ferritic stainless steel.
  • the molten steel is a molten steel containing 10 to 23% by mass of chromium and 0.005 to 0.010% by mass of Mg.
  • the Mg content is less than 0.0005% by mass, the amount of MgO in the molten steel decreases, solidification nuclei are not sufficiently generated, and the pinning effect is weakened, so that the solidification structure cannot be made fine.
  • the Mg content exceeds 0.010% by mass, the effect of refining the solidified structure is saturated and no remarkable effect is exhibited, and the amount of Mg, Mg-containing alloy, etc. used increases and the production increases. The construction cost increases.
  • the chromium content is less than 10% by mass, the corrosion resistance of the steel pipe is reduced and the effect of refining the solidified structure is reduced. If the chromium content exceeds 23% by mass, the amount of chromium alloy to be added increases and the production cost increases.
  • the continuous forming method of the present invention when applied to the continuous forming of molten steel of a fly-based stainless steel, the molten steel may be stirred while being stirred by an electromagnetic stirrer.
  • the tip of the columnar crystal generated during solidification is cut off, and the solidification structure of the piece can be made finer by the suppression of the growth of the columnar crystal and the interaction of the solidification nuclei by the divided fragments.
  • the center porosity caused by solidification and shrinkage of the unsolidified portion remaining inside the piece can be press-bonded, and the center segregation caused by the flow of unsolidified molten steel can be prevented. so Wear.
  • the solid phase ratio is reduced from a range of less than 0.2, there is too much unsolidified area, so that even when the solid content is reduced, the crimping effect cannot be obtained and the brittle solidified shell may crack. If the solid phase ratio is reduced from a range larger than 0.7, the center porosity may not be pressed. In addition, a large rolling force is required to crimp the one-port center city, and the rolling device becomes larger.
  • a seamless steel pipe according to the present invention which meets the above-mentioned object, comprises: pouring molten steel containing 10 to 23% by weight of chromium and adding 0.0005 to 0.010% by weight of Mg into a mold; It is manufactured by perforating a piece that has been continuously manufactured while solidifying by cooling and cooling by spraying water from a cooling water nozzle laid on the support segment in a pipe making process.
  • this steel pipe uses fine pieces with a solidified structure, cracks and dents on the surface and inside of the pipe are suppressed during drilling in the pipe making process, and no maintenance such as grinding is required. It is a good quality steel pipe.
  • FIG. 1 is a sectional view of a continuous manufacturing apparatus for manufacturing a piece according to the present invention.
  • FIG. 2 is a cross-sectional view of the continuous manufacturing apparatus shown in FIG.
  • FIG. 3 is a cross-sectional view of the — type shown in FIG.
  • FIG. 4 is a sectional view taken along line AA of the continuous manufacturing apparatus shown in FIG.
  • FIG. 5 is a sectional view of a processing apparatus used in the method for processing molten steel of the present invention.
  • FIG. 6 is a cross-sectional view of another processing apparatus used in the method for processing molten steel of the present invention.
  • Figure 7 is a schematic diagram of the solidification structure in the thickness direction of a conventional piece.
  • FIG. 8 is a diagram showing the relationship between the distance from the surface layer and the equiaxed crystal diameter and the width of the columnar crystal in the piece of the present invention.
  • FIG. 9 is a schematic view of a solidified structure in a thickness direction of a piece of the present invention
  • FIG. 10 is a view showing another relationship between a distance from a surface layer and a equiaxed crystal diameter of the piece of the present invention.
  • FIG. 11 is a diagram showing another relationship between the distance from the surface layer, the equiaxed crystal diameter, and the width of the columnar crystal in the piece of the present invention.
  • FIG. 12 is a diagram showing another relationship between the distance from the surface layer and the equiaxed crystal diameter in the piece of the present invention.
  • FIG. 13 is a sectional view in the thickness direction of the piece of the present invention.
  • FIG. 14 is a view showing the relationship between the distance from the surface layer of the piece of the present invention and the maximum grain size Z average grain size related to the crystal grain size.
  • FIG. 15 is a diagram showing the relationship between the distance from the surface layer of a conventional piece and the maximum grain size average grain size related to the crystal grain size.
  • FIG. 16 is a diagram showing the relationship between the number of inclusions of 10 / zm or less (pieces Zcm 2 ) and the equiaxed crystal ratio (%) in each piece.
  • CaO- A 1 2 0 3 - in the state diagram of gO system is a diagram showing the composition region according to the present invention.
  • FIG. 18 is a diagram showing the relationship between the solubility product of the Ti concentration and the N concentration / in the molten steel: [% Ti] X [% ⁇ ] and the concentration [% Cr] in the molten steel processing method of the present invention. .
  • FIG. 20 is a view showing the relationship between the basicity of slag and the activity of Ca 0 in the method for treating molten steel of the present invention.
  • a continuous forming apparatus 10 used for manufacturing a piece according to the present invention includes a tundish 12 for storing molten steel 11 and a molten steel 11 from the tundish 12 to a mold 13.
  • An immersion nozzle 15 provided with a discharge port 14 for pouring molten metal, an electromagnetic stirrer 16 for stirring the molten steel 11 in the mold 13, and a support segment for solidifying the molten steel 11 by spraying water from a cooling water nozzle (not shown). 17, a pressing segment 19 for pressing down the central portion of the piece 18, and pinch rolls 20 and 21 for pulling out the pressed piece 18.
  • the electromagnetic stirrer 16 is provided outside the long pieces 13a and 13b of the ⁇ type 13, the electromagnetic coil 16a is provided on the long piece 13a side, and the electromagnetic coil is provided on the long piece 13b side. 16c and 16d are arranged.
  • this electromagnetic stirring device 16 is used as needed.
  • the pressing segment 19 is composed of a supporting roll 22 for holding the lower surface of the piece 18 and a pressing roll 24 having a convex portion 23 that contacts the upper surface of the piece 18.
  • the pressing roll 24 is pressed down by a hydraulic device (not shown), the convex portion 23 is pushed to a predetermined depth position, and the unconsolidated portion 18b of the piece 18 is pressed down.
  • reference numeral 18a denotes a solidified shell of the piece 18.
  • the piece 18 is then cut into a predetermined size, conveyed to a subsequent process, heated in a heating furnace (not shown), a soaking furnace, or the like, and then subjected to a process such as rolling to form a steel material.
  • a heating furnace not shown
  • a soaking furnace or the like
  • FIGS. 5 and 6 show a processing apparatus used in the processing method of the present invention.
  • a processing apparatus 25 shown in FIG. 5 includes a ladle 26 receiving molten steel 11, a hopper 27 provided above the ladle 26 for storing an A1-containing alloy, and sponge Ti, Fe—Ti alloy, and the like. Ti alloy, or Fe—N alloy, N—Mn alloy, N— A hopper 28 for storing an N alloy such as a Cr alloy, and a shot 29 for adding the alloy from the storage hoppers 27 and 28 to the molten steel 11 in the ladle 26 as necessary are provided.
  • the treatment device 25 guides the wire 30 formed by covering the metal Mg with the iron pipe into a linear shape with the guide pipe 32, and supplies the wire 30 into the molten steel 11 through the slag 33.
  • a supply device 31 is provided.
  • reference numeral 34 denotes a porous plug for supplying an inert gas to the molten steel 11 in the ladle 26.
  • the processing apparatus 35 shown in FIG. 6 includes a ladle 11 and a lance 36 for blowing Mg or Mg alloy powder.
  • a lance 36 is immersed in molten steel U, which is housed in a ladle 26 and has a slag 33 formed on the surface, and from this lance 36, for example, corresponds to 0.0005 to 0.010 mass% of Mg content.
  • a small amount of Mg or Mg alloy powder is blown with an inert gas.
  • the solidified structure of the ⁇ piece is a chill crystal with a fine crystal structure that is rapidly cooled by the ⁇ type and solidified on the surface layer (surface layer part), and formed inside the chill crystal. It consists of columnar crystals with a large crystal structure.
  • equiaxed crystals may be formed inside the pieces, or columnar crystals may reach the center.
  • steel products manufactured from ⁇ pieces having a solidified structure with a large proportion of columnar crystals are inferior to steel materials manufactured from ⁇ pieces with fine equiaxed crystals, and have surface defects such as wrinkles. It is easy to occur.
  • D is the diameter of the equiaxed crystal as a structure having the same crystal orientation (), and X is the distance (mm) from the surface of the piece.
  • piece A of the present invention a piece having a solidified structure having an equiaxed crystal satisfying the above equation is piece A of the present invention.
  • the diameter of this equiaxed crystal is specified by the brightness of the reflected light according to the crystal orientation of the macrostructure when the entire cross section in the thickness direction of the piece of solidified molten steel is etched and light is applied to the surface. To detect the diameter of this equiaxed crystal, it is necessary to cut the piece in such a way that a section in the thickness direction of the piece comes out and polish the section. (A mixture of an acid and an alcohol).
  • the average equiaxed crystal size is determined from the equiaxed crystal size (mm) obtained by taking a macro structure in a 1- to 100-fold enlarged photograph and processing the enlarged photograph.
  • the largest of the equiaxed crystal diameters is the largest equiaxed crystal diameter.
  • FIG. 8 shows the relationship between the distance from the surface layer and the equiaxed crystal diameter in piece A of the present invention. 60
  • 60 By making 60% or more of the entire cross section of the piece a solidified structure with equiaxed crystals satisfying the above formula, columnar crystals in the surface layer
  • the growth of columnar crystals in the surface layer was suppressed,
  • the brittle micro-mouth segregation is small and even very small. Therefore, even if shrinkage or uneven stress occurs during cooling or solidification by the mold, the surface defects such as cracks and dents generated from the micro-mouth segregation part can be prevented. The occurrence is suppressed.
  • the equiaxed crystal diameter inside is also small, so that the micro-mouth eccentricity that occurs at the grain boundaries is small, as in the surface layer, and the resistance to cracking is small. As a result, it is possible to suppress the occurrence of internal cracks and the like caused by the distortion caused by the bulging of the piece and the bending back straightening.
  • the piece A has good processing characteristics and material, if a steel material is manufactured using the piece A, a steel material free from surface defects such as wrinkles can be obtained.
  • the equiaxed crystal satisfying the above formula is less than 60% of the total cross section of the piece, the range of the columnar crystal is increased and the inner equiaxed crystal diameter is increased, and the piece has cracks or dents. Occurs. As a result, ⁇ pieces need to be cared for or become debris.In addition, when the ⁇ pieces are processed, surface defects and internal defects occur in the steel materials, resulting in deterioration of the quality of the steel materials. Invite.
  • the solidified structure of the piece A of the present invention as shown in FIG. 10, by making the entire cross section of the piece an equiaxed crystal satisfying the above-mentioned formula, the solidified structure becomes a uniform solidified structure over the entire piece.
  • the brittle micro-segregation present at the grain boundaries can be reduced over the entire piece.
  • the ⁇ piece has increased resistance to cracking, and ⁇ even if shrinkage or uneven stress occurs during cooling or solidification due to the ⁇ mold, cracks or dents that occur from the microsegregation part as the starting point. Occurrence of surface defects and The generation of internal cracks and the like due to the strain caused by the jing-bending correction is reliably suppressed.
  • solidification starting from the solidification nucleus can reduce the equiaxed crystal diameter, resulting in improved flow of molten steel immediately before solidification is completed, resulting in center porosity (Zaku) and center segregation due to contraction of molten steel. Such defects can be prevented, and a piece without defects can be manufactured.
  • the maximum equiaxed crystal size by setting the maximum equiaxed crystal size to be no more than three times the average equiaxed crystal size, a favorable result can be obtained by further reducing the solidification structure. .
  • the uniformity of the deformation behavior is further improved during processing such as rolling.
  • the maximum equiaxed crystal diameter is more than three times the average equiaxed crystal diameter, local local deformation of the work becomes non-uniform and strip-like wrinkles may occur in the steel material.
  • the piece A of the present invention paying attention to the diameter of the equiaxed crystal obtained by image processing, as shown in FIG. 11, 60% or more of the entire cross section of the piece satisfies the following formula. It can be equiaxed, and a favorable solidification structure can be obtained.
  • X is the distance (mm) from the surface of the piece and D is the diameter (mm) of the equiaxed crystal at the distance of X from the surface of the piece.
  • the entire cross section of the piece can be made into an equiaxed crystal satisfying the above equation, and the solidification structure You get something better.
  • Mg or Mg alloy is added to the molten steel 11 in the tundish 12 so that the molten steel 1 A single MgO or a composite oxide containing MgO (hereinafter referred to as “MgO-containing oxide”) is formed in 1.
  • MgO has good dispersibility, becomes fine grains, and is uniformly dispersed in molten steel 11 to act as solidification nuclei.
  • the oxide itself pinning (suppresses the coarsening of the solidification structure immediately after solidification) ) Acts to suppress the coarsening of the solidified structure, to form equiaxed crystals, to make the equiaxed crystals themselves finer, and to make the pieces homogeneous.
  • the amount of Mg or Mg alloy to be added is equivalent to Mg and is sufficient to add 0.0005 to 0.10% by mass of the molten steel to the molten steel, but the added Mg is added to the oxygen in the molten steel. and, F e O, reacts with oxygen supplied from the S i 0 2, oxides such as MnO, MgO or MgO-containing oxides are formed.
  • the method of adding Mg or Mg alloy is to directly add Mg or Mg alloy to molten steel, or to continuously supply Mg or Mg alloy with a wire covered with thin steel and processed into a wire shape.
  • the amount of Mg added is less than 0.0005% by mass, the number of solidified nuclei is insufficient, and the number of generated nuclei is insufficient, so that it is difficult to obtain a fine solidified structure.
  • the piece manufactured in this way has a uniform and fine solidification structure, extremely few surface defects and internal defects, and has good processing characteristics.
  • the piece A of the present invention can be produced by a method of ingot making, a belt caster, a double mouth, or the like, in addition to the continuous production. Next, a steel material manufactured from the piece A of the present invention will be described.
  • a piece A having an equiaxed crystal solidification structure in which 60% or more of the entire cross-section of the solidification structure satisfies the following formula was obtained by a heating furnace (not shown), a soaking furnace, or the like. After being heated to 250 ° C, it is manufactured by rolling and other processing (for example, steel sheets and section steels).
  • D is the diameter (mm) of the equiaxed crystal as a structure having the same crystal orientation
  • X is the distance () from the surface of the piece.
  • this steel material is manufactured from piece A having the above solidified structure, brittle micro-deflection present at the grain boundaries is small, and the crack resistance of the micro-mouth segregated portion is increased, and Steel with few surface defects
  • the piece A of the present invention has high uniformity of deformation during processing such as rolling and is excellent in processing characteristics, the steel material is excellent in material such as toughness and wrinkles. There are few surface defects such as cracks.
  • steel pieces manufactured by applying a process such as rolling after heating using a piece having an equiaxed crystal that satisfies the above equation are used as pieces having a uniform solidification structure. Since surface defects and internal defects are extremely small and the uniformity of deformation during processing is better, the processing characteristics and materials are excellent.
  • the maximum equiaxed crystal diameter of the piece is controlled to be within three times the average equiaxed crystal diameter, the magnitude of micro-distortion formed at the boundary of the equiaxed crystal diameter is suppressed. It is possible to obtain steel with more uniform material properties. Wear.
  • the piece B of the present invention is characterized in that the maximum value of the crystal grain size at an equal depth from the surface of the piece is within three times the average crystal grain size at that depth. I do.
  • the depth ai K equal to the surface of the piece 18, for example, the maximum value of the crystal grain size at a position of 2 to 10 mm is the same depth a
  • the average grain size in mm is set to 3 times or less, the formation of coarse columnar crystals on the surface layer is suppressed, and the segregation of grain boundaries such as Cu and other trap elements is suppressed. Less.
  • the occurrence of dent flaws or cracks due to uneven cooling or solidification shrinkage is prevented, and the structure of the piece can be made into a tissue having high resistance to cracking.
  • the value of the crystal grain size at the same depth a mm from the surface of the piece for example, the value obtained by measuring the crystal grain size of the exposed surface after grinding to a position of 2 to 10 mm from the piece surface is Used. This grinding may be performed up to the vicinity of the center of the piece.
  • the maximum value of the crystal grain size is set to be within three times the average crystal grain size at the same depth, and When at least 60% or more of the entire cross section of the piece is made to be equiaxed, formation of coarse columnar crystals in the surface layer as shown in FIG. 9 can be suppressed, and a uniform structure can be obtained throughout.
  • FIG. 15 shows the relationship between the distance from the surface layer of the conventional piece and the maximum grain size Z average grain size of the crystal grain size.
  • the piece B of the present invention When the piece B of the present invention is processed, the concentration of deformation strain on specific crystal grains is suppressed, and the isotropy of the deformation behavior (elongation in the width direction and the length direction due to reduction) is secured. Therefore, the piece B of the present invention has higher workability.
  • segregation at the grain boundaries such as a trap element formed at the grain boundaries can be reduced, and the cracking resistance against cracking at the time of rolling or other rolling reduction can be further increased. The occurrence of defects such as cracks in the steel material is prevented.
  • the grain boundary segregation is reduced by forming a structure with fine and uniform crystal grains throughout.
  • the quality and material such as r-value (drawing characteristics) and toughness of steel material can be improved by increasing the isotropy of the processed deformation.
  • the crystal grain size is the grain size (mm) of a structure with the same crystal orientation.
  • the surface of the piece is etched and specified by the brightness of the reflected light according to the crystal orientation of the macrostructure. Is the size of the coagulated tissue.
  • the detection of the crystal grain size is performed by cutting the solidified piece into a predetermined length so that a cross section in the thickness direction of the piece comes out, grinding the outer circumference to a predetermined depth, and polishing the exposed surface.
  • etching is performed by reacting with hydrochloric acid or nital (a mixed solution of nitric acid and alcohol), and the macrostructure is taken in an enlarged photograph of 1 to 100 times, image processed, and the crystal grain size is measured. Then, find the maximum diameter and average value.
  • Mg or a Mg alloy is added to the molten steel 11 in the tundish 12 (see FIGS. 1 and 2), and To form MgO alone or MgO-containing oxide.
  • the piece B of the present invention can be manufactured not only by continuous forming, but also by an ingot forming method, a belt caster, a twin-roll or other such forming method.
  • the piece B of the present invention is heated to 1150 to 1250 ° C by a heating furnace and a soaking furnace (not shown), and then subjected to a process such as rolling to obtain a steel material such as a steel plate or a shaped steel. You.
  • This steel material has few surface defects such as cracks and scabs, and few internal defects such as internal cracks, and has excellent processing characteristics.
  • At least 60% of the section in the thickness direction of the piece is equiaxed.
  • the number of defects is further reduced, and a steel material having excellent processing characteristics, for example, drawing characteristics, can be obtained.
  • the molten steel (ferritic stainless steel molten steel containing 13 mass% of chromium) whose solidification primary crystal (the phase that crystallizes first when molten steel 11 solidifies) is 5 ft.
  • the molten metal is poured from the immersion nozzle 15 provided in the tundish 12 into the mold 13 (see FIGS. 1 and 2), and cooled to form a solidified shell 18 a, forming a piece 18, and a supporting segment 17. As it proceeds downward, the heat is removed by the cooling water that is sprayed, and while the thickness of the solidified shell 18a is gradually increased, it is reduced by the reduction segment 19 on the way (see FIG. 4), and is completely solidified.
  • the conventional solidification structure in the cross section in the thickness direction of a piece has a fine structure, which is rapidly cooled by a mold and solidified in the surface layer (surface portion) of the piece.
  • a large columnar crystal is formed inside the chill crystal.
  • micro-segregation exists at the boundary of columnar crystals, and the micro-fractionation site has fragile properties. It may cause surface defects such as cracks and dents.
  • This micro-segregation has the same fragile properties as the surface layer, and mechanical reactions such as heat shrinkage when the inside solidifies, fragment bulging, and straightening. It is the starting point for internal cracking due to force.
  • the metal is in the molten steel, C, N, S, inclusions and reacts with S i 0 2 or the like, or inclusions added in molten steel, 10 / zm inclusions below the molten steel To form These inclusions act as solidification nuclei when the molten steel solidifies, and serve as starting points for solidification.
  • the growth of the solidified structure is suppressed by the pinning action of the inclusion, and a piece having a fine solidified structure can be obtained.
  • stirring by the discharge flow of the molten steel 11 in the mold 13 or stirring by the electromagnetic stirring device 16 causes 100 inclusions with a size of 10 m or less /
  • the size of cm 2 or more is formed, the solidification nucleus and the pinning action thereof are more remarkably developed, and as shown in FIG. 16, a piece having a solidification structure with an equiaxed crystal ratio of 60% or more can be obtained.
  • Figure 9 shows the solidification structure in the cross section in the thickness direction of the piece, and a fine equiaxed crystal structure was formed inside the piece. In the layer, the growth of columnar crystals is suppressed.
  • the solidification structure of the entire cross section from the surface layer portion of the piece to the inside can be made into a finer and more uniform equiaxed crystal.
  • the piece C of the present invention having a fine equiaxed crystal has a high cracking resistance, so that surface defects such as cracks and dents generated on the surface of the piece are less likely to occur.
  • the inside of the piece C of the present invention has few brittle micro-segregation portions, and even if heat shrinkage or some stress occurs, there is little occurrence of internal cracks and the like, and the molten steel immediately before solidification is completed. The occurrence of internal defects such as center porosity and center segregation due to supply shortage is also prevented.
  • the piece when the piece is subjected to a process such as rolling, the fine equiaxed crystal in the piece C of the present invention is easily deformed in the rolling direction, so that the piece C of the present invention has more processing characteristics. It is expensive.
  • inclusions which are metal compounds
  • metals and metal compounds such as Mg, Mg alloys, ⁇ Ce, Ca, and Zr are used.
  • C, N is reacted with S and Si0 oxide such as 2.
  • MgO, MgAl 2 0 4, TiN, CeS, Ce 2 0 3, CaS, Zr0 2, TiC, the VN and the like the lattice mismatch between the (full Werai Bok 6 if% below those used. from the stability of generation of the dispersibility and coagulation nuclei when added to molten steel, particularly, MgO, gAl 2 0 4, TiN is not to prefer.
  • the degree of lattice mismatch with ferrite is the value obtained by dividing the difference between the lattice constant of ⁇ 5 ferrite formed by solidification of molten steel and the lattice constant of a metal compound by the lattice constant of solidification nuclei of molten steel. The smaller the value, the better the formation of solidification nuclei.
  • the size of the metal compound observe the inclusions on all cross-sections using an electron microscope such as a SEM and average the maximum and minimum diameters of each inclusion to determine the size of the inclusions.
  • the slime method a part of the entire cross section of the piece is cut out, the cut piece is melted, then the inclusions are classified and taken out, and the maximum diameter and the minimum diameter of each inclusion are determined.
  • the size is determined by averaging the values, and the number for each size is determined.
  • the molten steel 11 in the evening dish 12 must be prepared by adding oxygen, FeO, Si0 2, MnO, nitrogen reacts with carbon and the like, MgO, MgAl 2 0 4, TiN, or the addition of a metal which forms inclusions TiC, etc., or directly to, the addition of these inclusions.
  • Mg or an Mg alloy to the molten steel to form inclusions composed of MgO alone or an oxide containing MgO in the molten steel because the dispersibility of the inclusions in the molten steel can be improved.
  • Mg or Mg alloy is added so that 0.0005 to 0.10% by mass of Mg is added to molten steel.
  • the method of addition is to add Mg or Mg alloy directly to the molten steel, or to continuously form a wire formed by covering the Mg or Mg alloy with thin steel and forming a wire. (See Figures 5 and 6).
  • molten steel of a steel type having a solidification primary crystal of (5 frites) for example, there is SUS stainless steel containing 11 to 17% by weight of chromium.
  • the piece C of the present invention has a uniform and fine solidified structure, suppresses the occurrence of surface defects and internal defects, and has excellent processing characteristics.
  • the piece C of the present invention can be produced by a method of ingot making, a belt caster, a twin roll, or the like, in addition to the continuous production.
  • Piece C of the present invention is pulled out by pinch rolls 20 and 21 (see FIG. 1), cut into a predetermined size by a cutting machine (not shown), and then conveyed to a post-process such as rolling.
  • the piece C of the present invention is heated to 115 to 1250 ° C. by a heating furnace, a soaking furnace, or the like (not shown), and then subjected to a process such as rolling.
  • This steel material has strong microstructure crack resistance and has few surface defects such as cracks and scabs generated during and after processing.
  • the steel material suppresses center segregation and the like in the inside of the piece, there are few internal defects generated due to the internal defect of the piece during processing.
  • the strip C of the present invention having a fine and uniform solidified structure has an r value of It has excellent processing characteristics, such as easy processing of a piece and excellent toughness of the weld after processing.
  • a steel material manufactured by subjecting a piece, which has a good dispersibility and a large number of inclusions having a size of lO ⁇ m or less to a process such as rolling, to a flaw generated on the surface of the steel material In addition to the fact that the occurrence of cracks and the like is reliably prevented, it is easily deformed in the rolling direction, so that the processing characteristics such as elongation are higher.
  • the piece D of the present invention is a piece manufactured by adding a metal or a metal compound that forms a solidification nucleus to the molten steel during solidification of the molten steel, and the size contained in the surface layer of the piece is 10 m.
  • the number of metal compounds having a size of 10 / zm or less contained from the surface layer portion is 1.3 times or more the number of the following metal compounds.
  • a metal that reacts with 0, C, N, oxide, or the like in molten steel to form a metal compound, or the metal compound itself. Is added to the molten steel so that when the molten steel solidifies, solidification nuclei are formed.
  • metal compounds of various sizes are formed in the molten steel, and when the size of the metal compound exceeds 10 m, it is difficult to form solidification nuclei, and coarsening of equiaxed crystals due to the pinning action of the metal compound itself. The effect of preventing solidification is not fully exhibited, and the coagulated structure cannot be miniaturized.
  • the number of metal compounds having a size of 10 m or less must be at least 1.3 times as many as those present in the surface of the piece.
  • the function as solidification nuclei and the pinning action make the equiaxed crystal. It promotes miniaturization, suppresses coarsening of equiaxed crystals, and obtains a solidified structure having uniform and fine equiaxed crystals.
  • a piece having a solidified structure in which more than 60% of the solidified structure in the cross section in the thickness direction of the piece is a fine equiaxed crystal and the columnar crystals in the surface layer are suppressed to be small is obtained.
  • the piece D of the present invention suppresses the generation of cracks and dents due to distortion and stress in the solidification process, and the generation of surface defects caused by inclusions, and the like.
  • the resistance to internal cracking due to the applied strain is strengthened, and the fluidity of the molten steel is ensured, so that the occurrence of internal defects such as center porosity and center segregation is suppressed. .
  • the number of metal compounds serving as solidification nuclei is small in the surface layer and large in the inside, so that when the piece is processed into a steel sheet such as a thin plate or a section steel.
  • the generation of surface defects such as dents and cracks on the surface due to inclusions is suppressed, and the metal compound is exposed to the surface of a thin plate, section steel, etc., or is present near the surface layer. This also prevents the corrosion resistance from decreasing.
  • MgO, gAl 2 0 4 TiN, Ce S, Ce 2 0 3, CaS, Zr0 2, TiC, lattice mismatch Godo with ⁇ full Werai Bok of VN or the like 6%
  • MgO, gAl 2 0 4, TiN is more preferred correct o
  • a metal to be added to the molten steel a metal such as Mg, an Mg alloy, Ti, Ce, Ca, or Zr is used. 0 and C in the molten steel, reacts with the oxide of N, Si0 2 or the like, but to use those to form the metal compound, it is also possible to use metal compounds comprising the same, such as a metal.
  • molten steel 11 in a tundish 12 (see FIGS. 1 and 2), Mg, Mg alloy, Ti, Ce, Ca, It was added Zr or the like, oxygen in the molten steel 11, or,, FeO, Si0 2, MnO, nitrogen, is reacted with carbon or the like, MgO, MgAl 2 0 4, TiN, TiC, to form the metal compound and the like.
  • Mg or an Mg alloy is added to molten steel to form MgO alone or an oxide containing MgO in the molten steel, the dispersibility of the metal compound in the molten steel is improved. Good results are obtained.
  • Mg or an Mg alloy is added so that 0.0005 to 0.010 mass% of Mg is added to molten steel.
  • the method of addition is to add Mg or Mg alloy directly to the molten steel, or to continuously supply a wire formed by covering the Mg or Mg alloy with thin steel and forming a wire (see Figs. 5 and 6). ).
  • the added amount of Mg is less than 0.0005% by mass, the absolute amount of solidification nuclei is insufficient, the solidification nuclei and the pinning effect are reduced, and it is difficult to obtain a fine solidified structure.
  • ⁇ D of the present invention thus is ⁇ the solidified structure is uniform, the generation of surface defects and internal defects have been suppressed, and a good processing properties c
  • the piece D of the present invention can be manufactured by an ingot forming method, a belt caster, a twin roll or other manufacturing method in addition to the continuous manufacturing.
  • inclusions metal compounds
  • the equiaxed crystal in the solidified structure from the surface layer to the inside can be easily adjusted, so that favorable results can be obtained.
  • a structure formed by a vertical or curved continuous structure using a mold having both ends penetrated has a greater effect of miniaturization, and a favorable result can be obtained.
  • the piece D of the present invention is heated to 115 to 1250 ° C. by a heating furnace and a soaking furnace (not shown), and then subjected to processing such as rolling to be processed into a steel material such as a thin plate or a section steel. You.
  • this steel material Since this steel material has an increased cracking resistance at the micro segregation portion inside the piece, it is a steel material with few surface defects such as cracks and scabs. Furthermore, even within the steel material, the occurrence of internal defects such as internal defects due to internal defects of the piece and internal cracks due to processing such as rolling is extremely small. Furthermore, since the piece D of the present invention has good processing characteristics and corrosion resistance, a steel material produced by processing the piece D also has good processing characteristics and corrosion resistance.
  • the processing method I of the present invention is characterized in that the total Ca of molten steel is set to 0.0010% by mass or less, and then Mg is added to the molten steel.
  • the total amount of Ca including Ca or CaO contained in the molten steel is 0.0010% by mass or less (sometimes 0). It is adjusted to become. Moreover, so that A 1 2 0 3 and a low melting compound of CaO (mixed oxide) in a calcium aluminate one preparative (12CaO ⁇ 7 A1 2 0 3 ) is not generated.
  • Et al is, MgO Chikaraku generated by the addition of Mg or Mg alloy, CaO - A1 2 0 a composite oxide and bonded with low melting point CaO- A 1 2 0 3 3 ternary double engagement oxidation of -MgO of Form an object. Since this composite oxide melts in the temperature range of molten steel, it does not function as a solidification nucleus, and as a result, a fine solidification structure cannot be obtained. Alternatively, even if the composite oxide is an inclusion having a relatively high melting point, since it contains CaO, it has low lattice mismatch with the ⁇ 5 filler and does not act as a solidification nucleus.
  • the added amount of Mg or Mg alloy is 0.0005 to 0.10 mass% in terms of Mg. This is because if the added amount of Mg is less than 0.0005% by mass, the solidification nuclei to be formed are insufficient, and it becomes difficult to obtain a fine structure. This is because the effect is saturated and the total amount of oxides inside the piece increases and the corrosion resistance and the like decrease. Also, the alloy cost increases.
  • the oxygen supplied from the molten steel or the oxygen supplied from oxides such as FeO, SiO 2 , and MnO is reduced.
  • Formed composite oxide of A 0 3, etc., these oxides are uniformly dispersed in the solvent steel and finely divided.
  • the total amount of Ca contained in the amount or molten steel Mg, the processing unit 25, 35 (FIGS. 5 and 6, reference) is adjusted in, calcium Arumine preparative (1 2CaO ⁇ 7 A 1 2 0 3 and low It is preferably adjusted so as to suppress the generation of the melting point compound).
  • oxygen and contained in the molten steel FeO, by Si0 2, oxygen supplied from oxides such as MnO, to form a unitary or MgO ⁇ A1 2 0 MgO-containing oxides such as 3 of MgO, fine Oxides in the molten steel
  • the solidified structure of the piece obtained by continuously forming the molten steel treated by the treatment method I of the present invention has a solidified structure composed of uniform and fine equiaxed crystals. Become.
  • the piece manufactured in this manner is cut into a predetermined size, conveyed to a subsequent process, heated in a heating furnace (not shown), a soaking furnace, or the like, and then subjected to processing such as rolling. It is manufactured in. Since the workability of this piece is greatly improved, the steel material manufactured from this piece has excellent drawability and toughness.
  • the piece can be manufactured by a method other than continuous manufacturing, such as an ingot-making method, a belt caster, or a twin roll.
  • a method other than continuous manufacturing such as an ingot-making method, a belt caster, or a twin roll.
  • continuous manufacturing such as an ingot-making method, a belt caster, or a twin roll.
  • the processing method (2) of the present invention is characterized in that before adding a predetermined amount of Mg to molten steel, a predetermined amount of an A1-containing alloy is added to the molten steel to perform a deoxidizing treatment.
  • the molten steel 11 (150 tons) after the decarburization scouring is put in the ladle 26 to adjust the components, and then the molten steel 11 is charged with the A1 from the storage hopper 27 to 70 kg cut out, added from shoot 29, and at the same time, argon gas was supplied from porous plug 34 provided at the bottom of ladle 26, and while molten steel 11 was stirred, molten steel 11 was sufficiently deoxidized by added A1. I do.
  • argon gas is continuously supplied from the porous plug 34, and the rotating drum (not shown) of the supply device 31 is operated to send out the wire 30 while guiding it through the guide pipe 32, and penetrate the slag 33, Supply 0.75 to 15 kg of metal (0.0005 to 0.010 mass%) into molten steel 11 ⁇
  • molten steel contains a large number of dispersed MgO and oxides containing Z or MgO, and during solidification, solidification starts at many points starting from these oxides. become.
  • cracks and dents generated on the surface of the piece can be eliminated, and center segregation and center porosity generated inside can be suppressed.
  • the quality can be improved by suppressing the care and scrapping of the processed steel material.
  • the TiN also act in the same manner as in coagulation nuclei, MgO and / or MgO - the synergistic effect with the A 1 2 0 3, as possible out to the fine coagulation tissue.
  • the order of addition of A1 and Ti in addition to the order of addition, Ti previously and to generate Ti0 2 by adding, followed by the added A1, and based on changing the Ti0 2, the reduced Ti It may be dissolved in molten steel.
  • Ti can form TiN on the MgO-containing oxide or by itself to further improve the function as a solidification nucleus. And, since Ti may be added in a small amount, alloy cost can be reduced and defects caused by TiN can be prevented.
  • a part of the molten steel treated by the treatment method ⁇ of the present invention was sampled, and the composition of the MgO-containing oxide was investigated by using an electron probe microanalysis (EPMA) method using an electron microscope.
  • EPMA electron probe microanalysis
  • Et al is, the addition of Ti from the addition of A1, in then case of adding Mg, the surface of the A 1 2 0 3 was coated MgO-containing oxides, and La, one the outer circumference An inclusion with a structure covered by TiN was observed, but this inclusion acts as an effective solidification nucleus because the degree of lattice mismatch with the filler is less than 6%.
  • the piece of molten steel produced by the treatment method of the present invention has a sufficiently fine surface layer portion and a solidified structure inside in the section of the piece. .
  • oxides such as slag and deoxidation products contained in the molten steel and oxides generated when Mg is added to the molten steel are as follows: It is preferable to add a predetermined amount of Mg to molten steel so as to satisfy equations (2) and (3).
  • k represents mol% of the oxide.
  • MgO 'A 1 2 0 3 ⁇ CaO -based oxide is Or an MgO.CaO-based high melting point oxide or the like is formed.
  • MgO 'Al 2 0 3 ⁇ CaO -based oxide is because it is a low melting point, when the molten steel solidifies, does not act as a solidification nucleus.
  • MgO'CaO-based oxides exist in a solid state because of their high melting points, but do not act as solidification nuclei because of poor lattice matching with primary solids of S-Finitrite.
  • the present inventors for which like MgO ⁇ A 1 2 0 3 ⁇ CaO -based oxide ⁇ beauty MgO * CaO-based oxide of a result of extensive studies, the molar fraction of the composition of the oxides It has been found that, when the ratio is within an appropriate range, it is possible to suppress the lowering of the melting point of this oxide and to improve the degree of lattice mismatch with 5 ferrite, which is the primary solidification crystal.
  • the amount of Mg to be added is determined in consideration of the yield so that the value becomes 500 or less, and while supplying the Mg wire 30 corresponding to this value through the guide pipe 32, the supply device 31 is operated to supply the molten steel 11 to the molten steel 11. Was added.
  • CaO- A 1 2 0 3 - shows a ternary phase diagram of the MgO, that exist in the (3) in the area in the figure satisfying the (range hatched surrounded by .smallcircle) CaO - if a composite oxide of a 1 2 0 3 -MgO system, acts effectively as a solidification nucleus.
  • the ⁇ value exceeds 500, even if the composite oxide has a low melting point or a high melting point, the amount of the MgO-containing oxide covering the surface of the oxide is reduced and the oxide does not act as a solidification nucleus.
  • the value of / 3 is obtained by the following equation (4).
  • S value is less than 95, other oxides such as SiO 2 and FeO increase to inhibit the formation of a composite oxide that becomes a solidification nucleus.
  • k represents the mole (%) of the oxide. Therefore, the amount of Mg to be added is determined in consideration of the yield so that the ⁇ value becomes 500 or less and the value becomes 95 or more.
  • the supply device 31 While guiding the Mg wire 30 corresponding to the value of Mg obtained in this way through the guide pipe 32, the supply device 31 is operated and added to the molten steel 11.
  • the composite oxide is formed and dispersed in the molten steel. With the decrease in temperature, the molten steel 11 begins to solidify starting from these solidification nuclei, and equiaxed crystals are generated, resulting in a fine solidified structure. Can be manufactured.
  • the solidified structure of the piece obtained by solidifying the molten steel 11 becomes a fine solidified structure as shown in FIG.
  • a steel material processed into a piece with a fine solidification structure has good workability such as rolling, and the occurrence of surface defects such as edge flaws and pitting is stably prevented. .
  • the amount of Mg added be adjusted to a range corresponding to a concentration of 0.0005 to 0.010% by mass.
  • the Mg concentration is lower than 0.0005% by mass, a composite oxide having a lattice mismatch with 5F or less of 5% or less cannot be produced, and the solidified structure of the piece cannot be reduced.
  • the Mg concentration is higher than 0.010% by mass, the effect of refining the solidified structure is saturated, and the cost of adding Mg increases.
  • the treatment method III of the present invention is characterized in that a predetermined amount of Mg is added to molten steel having a Ti concentration and an N concentration satisfying a solubility product in which TiN is crystallized at a temperature higher than a liquidus temperature of molten steel.
  • the molten steel is made of ferrite-based steel.
  • the Ti concentration [% Ti] and the N concentration [% N] preferably satisfy the following equations.
  • [% Ti] is Ti mass% in molten steel
  • [% N] is N mass% in molten steel
  • [% Cr] is Cr mass% in molten steel.
  • the A1 2 0 3 contained in molten steel to 0.005 to 0.10 mass%.
  • the TIN has a good lattice mismatch of 4% with the S-plane (the difference between the lattice constant of TiN and the lattice constant of the 5-plane divided by the lattice constant of the 5-plane).
  • this TiN is easy to aggregate. Therefore, there is a problem that coarse ⁇ causes clogging of the immersion nozzle or causes defects such as sliver flaws of steel.
  • the MgO-containing oxide generated by adding Mg to the molten steel is characterized in that: The dispersibility is extremely good, and the TiN force ⁇ crystallizes preferentially on the MgO-containing oxide.
  • the present inventor paid attention to this point, and in the treatment method (2) of the present invention, the dispersibility of TiN acting as crystallization solidification nuclei on the MgO-containing oxide was enhanced by using the MgO-containing oxide.
  • a large number of solidification nuclei that are effective in refining the solidification structure are dispersed in molten steel.
  • the crystallization temperature of TiN is determined from the product of the Ti concentration and the N concentration, the so-called solubility product [% Ti] X [% N].
  • Ti and N added to molten steel are higher than the liquidus temperature of about 1500 ° C, and at 1506 ° C, which is higher than the crystallization temperature of TiN, solid solution
  • the present inventor conducted experiments focusing on the relationship between the solubility product of the Ti concentration and the N concentration and the concentration in order to refine the solidification structure of the stainless steel containing the required amount of Cr.
  • the results shown in Fig. 18 were obtained.
  • the above equation is obtained from the results shown in FIG.
  • X represents an example in which the solidified structure was not refined
  • ⁇ represents an example in which the solidified structure was sufficiently refined
  • ⁇ represents an example in which the solidified structure was refined.
  • this is an example where nozzle clogging occurred during fabrication.
  • molten steel 11 from which decarburization and removal of impurities such as phosphorus and sulfur had been taken was used to receive 150 tons of hot water in ladle 26 using a refining furnace.
  • This molten steel 11 is a bright stainless steel molten steel containing 10 to 23% by mass of Cr.
  • the Ti concentration 0 so that the Ti and N concentrations contained in the molten steel 11 satisfy the above formula. 020% by mass, N concentration: 0.024% by mass.
  • TiN has a low lattice mismatch of 5% with 5 fills, and is likely to be a solidification nucleus of 5 fills. And, when the molten steel solidifies, it is easy to generate equiaxed crystals and has an excellent effect of refining the solidification structure.
  • the crystallized TiN can be dispersed in the molten steel in a fine state.
  • Mg is added at a higher temperature than the crystallization temperature of TiN to generate an MgO-containing oxide.
  • the steel material obtained by processing flakes with a fine solidification structure has a fine solidification structure, so that the generation of surface defects such as hedging flaws, edge shim flaws, and mouth rubbing is also stable. It has been suppressed.
  • the processing method W of the present invention is characterized in that the slag covering the molten steel contains 1 to 30% by mass of an oxide reduced by Mg.
  • oxides reduced by Mg are FeO, Fe 2 0 3, nO and S i 0 2 of one or more Further, the processing method of the present invention in IV, the A1 2 0 3 contained in molten steel to 0.005 to 0.10 mass%.
  • the molten steel 11 subjected to the vacuum secondary refining (secondary refining) is received in a ladle 26.
  • MgO * Al promotes the formation of 2 0 complex oxides such as 3 is for forming a high melting point of MgO-containing oxides, in the et, likely A 1 2 0 3 aggregated poor dispersibility
  • the supply device 31 is operated to pass through the guide pipe 32, and the wire 30 of Mg or Mg alloy is penetrated into the molten steel 11 through the slag 33 at a speed of 2 to 50 mZ, and Mg is introduced into the molten steel 11. Added.
  • Mg or Mg alloy material is fed into the molten steel through the slag, a Mg yield of 10% or more can be achieved.
  • This Mg yield is the yield when all of the Mg and MgO-containing oxides contained in the molten steel are converted to the amount of Mg. Form of existence of Mg actually in molten steel, most of or single MgO, or a composite oxide such as MgO * Al 2 0 3.
  • Mg added to the molten steel is consumed by the chemical reaction shown in the above equations (1) to (4), and the generated MgO is transferred to the slag.
  • Ni will this Yo, increasing the yield of Mg added to molten steel, MgO, MgO - A1 allowed form 20 refractory composite oxides such as 3, to generate a good Ri stable fine coagulation Katakaku is
  • the oxide in the slag is preferably in the range shown by the following formula, and more preferably in the range of 2 to 20% by weight. Results are obtained.
  • alloys such as Si—Mg alloy, Fe—Si—Mg alloy, Al—Mg alloy, and Fe—Si_Mn_Mg alloy can be used.
  • the processing method V of the present invention is characterized in that before adding a predetermined amount of Mg to molten steel, the activity of CaO in the slag covering the molten steel is reduced to 0.3 or less.
  • the basicity of the slag is set to 10 or less.
  • vacuum secondary refining (secondary refining) was applied, carbon 0.01 to 0.05% by mass, manganese 0.10 to 0.50% by mass, chrome 10 to 20% by mass.
  • the molten stainless steel 11 containing was placed in the ladle 26.
  • slag 33 that is mixed in from the converter or generated by the flux or the like added in the secondary refining also flows in and covers the surface of the molten steel 11.
  • the slag 33 has a thickness of 50 to 100 mm, and its, CaO activity in slag 33 to 0.3 or less, also, basicity (CaOZSi0 2) in so that a 10 or less, off La It is adjusted by the addition of wax and the like.
  • the supply device 31 is operated and the slag 33 is guided at a speed of 2 to 50 m / min while guiding the Mg or Mg alloy wire 30 through the guide pipe 32.
  • the force converter contains an oxide such as FeO or secondary desulfurization and dephosphorization by refining, in slag
  • concentration of CaO may be increased.
  • the Ca concentration in the molten steel also increases due to the equilibrium reaction between the slag and the molten steel.
  • the CaO activity (aCaO) in the slag obtained from the following formula from the slag basicity is set to 0.3 or less.
  • Mg or Mg alloy must be added to molten steel.
  • Mg contained in Mg or Mg alloy, etc. such as MgO or Mg0-Al 2 0 3, a high melting point, and, (full E La
  • the oxide becomes an MgO-containing oxide with a small degree of lattice mismatch with the ingot, and acts sufficiently as a solidification nucleus when the molten steel solidifies, but the MgO-containing oxide also has a sufficient pinning effect. Since it is expressed, the solidification structure of the piece can be made finer, and the occurrence of surface defects and internal defects in the piece can be suppressed.
  • the CaO activity is 0.2 or less, the melting point of the generated MgO-containing oxide can be increased, and the function as a solidification nucleus can be further enhanced.
  • Mg contained in the added Mg or Mg alloy to form a CaO- A 1 2 0 3 low melting point composite oxides such as one MgO functions of the solidification nuclei Not only does it become a starting point for defects, but also hinders the quality of the piece or steel.
  • the CaO activity is 0.2 or less or the basicity is 6 or less, the formation of Mg0-containing oxides (acting as solidification nuclei) is promoted, and the pinning effect is further reduced.
  • the solidification structure of the piece can be reliably made finer.
  • alloys such as Si—Mg alloy, Fe_Si—Mg alloy, A1-Mg alloy, Fe—Si—Mn_Mg alloy, and Ni—Mg alloy are used.
  • the molten steel containing 0.0005 to 0.010% by mass of Mg is solidified in a mold to produce a compacted piece.
  • the pieces A to D of the present invention are manufactured by pouring molten steel containing an oxide containing MgO into a mold and continuously agitating the molten steel with an electromagnetic stirring device.
  • the electromagnetic stirrer is used for the meniscus in the mold. It will be installed within 2.5m downstream from the waste.
  • the flow rate of the stirring flow applied to the molten steel by the electromagnetic stirring device is set to 10 cmZ seconds or more.
  • molten steel 11 containing 16.5% by mass of chromium is poured into the mold 13 from the discharge port 14 of the immersion nozzle 15, cooled by the mold 13, and supported by the support segment. Cooling by cooling water nozzles attached to the cooling water nozzles 17 and forming solidified shells 18a, while solidifying them, pulls them out as pin pieces 18 by pinch rolls 20 and 21.
  • Chikaraku to contain mass% of Mg the Mg is oxygen and in the molten steel 11, and reacts with oxide such as Si0 2, MnO, to form MgO, a MgO ⁇ ⁇ 1 2 0 oxide such as 3 .
  • the Mg content is less than 0.0005% by mass, the amount of MgO in the molten steel is reduced, and the amount of solidified nuclei and the degree of pinning action are reduced, so that the solidified structure cannot be made fine.
  • the content of Mg exceeds 0.010% by mass, the effect of refining the solidified structure is saturated, so that a remarkable effect cannot be exhibited, and the cost of adding Mg and the like increases.
  • the electromagnetic stirring device 16 is arranged at a position 500 mm downstream from the molten metal surface (meniscus) in the mold 13.
  • the electromagnetic coils 16a and 16b apply a stirring flow from the short piece 13d to the short piece 13c along the inside of the long piece 13a of the rectangular shape 13, and the electromagnetic coils 16c and 16d cause the long piece 13b.
  • a stirring flow is applied from the short piece 13c to the short piece 13d along the inside.
  • a horizontal swirling agitated flow is applied to the molten steel 11.
  • the molten steel 11 poured from the discharge port 14 is cooled by the mold 13, and the oxide present in the vicinity of the solidified shell 18 a is washed away, thereby preventing the oxide from being captured by the solidified shell 18 a.
  • Surface layer with less oxide Can be.
  • this surface layer is cooled at a high cooling rate by cooling by the mold 13 and water spray from the cooling water nozzle attached to the support segment 17, a fine solidified structure is easily formed. Moreover, the agitation flow breaks the tip of the columnar crystal, and alleviates the so-called compositional supercooling (the melting point decreases locally due to the concentration of solute components accompanying the solid-liquid distribution at the solidification interface). Since it promotes equiaxed crystallization, a fine solidified structure can be obtained even with a small amount of oxide.
  • the oxide washed out from the vicinity of the solidified shell 18a partially floats and is trapped by powder (not shown) on the surface of the meniscus, but most of it remains inside the piece and becomes a solidified nucleus.
  • the inside of the piece can be made into a fine solidified structure.
  • the agitated flow to the molten steel 11 is generated by passing a three-phase alternating current having different phases through the electromagnetic coils 16a to 16d and applying a moving magnetic field known by Fleming's law to the molten steel 11 ( The strength of the thrust given by 5 to 90 rnmFe) is adjusted by changing the value of the current flowing through the electromagnetic coils 16 a to 16 d so that the flow velocity is adjusted to 10 to 40 cmZ seconds.
  • the steel material obtained by subjecting this piece 18 to rolling or the like also has a reduced surface and internal defects such as cracks, scabs, center porosity (Zaku) and center segregation, and is drawn. With excellent properties and material properties is there.
  • the fine solidification structure of the piece 18 is less than 60%, the crystal grains become large, surface defects and internal defects occur, and the material such as drawing characteristics deteriorates.
  • the solidified structure can be made more uniform, and the piece and the steel material can be obtained. Surface and internal defects can be more reliably prevented, and the material can be more stably improved.
  • the pieces manufactured in this manner contain a small amount of oxides in the surface layer portion, the amount of oxides existing on and near the surface of a thin plate or a shape steel that has been processed by rolling or the like can be reduced.
  • the amount of oxides on the surface or in the vicinity of the surface decreases, the amount of oxides (MgO-containing oxides) that elute when contacted with acids, salt water, etc. can be suppressed. Prevent corrosion. Therefore, a steel material obtained by processing a piece manufactured by the continuous manufacturing method of the present invention has excellent corrosion resistance.
  • the continuous manufacturing method of the present invention can be applied to continuous manufacturing of molten stainless steel.
  • molten steel 11 containing 10 to 23% by weight of chromium is poured into the mold 13 from the discharge port 14 of the immersion nozzle 15, While being agitated, the solidified shell 18a is formed by cooling by the mold 13 and cooling by spraying water from the cooling water nozzle attached to the support segment 17, and subsequently pinches as the piece 18 while solidifying. Pulled out by rolls 20, 21.
  • the molten steel 11 contains 0.0005 to 0.010% by mass of Mg. 0 is contained in the molten steel 1 1, S i 0 2, oxides of reacting with Mg 0 or MgO, such as MnO, and forms an oxide of a refractory, such as A l 2 0 3.
  • the MgO or MgO, oxides such as A l 2 0 3 acts as a solidifying nucleus promotes equiaxed crystallization solidification structure, and also so-called pin Nni ring acts to suppress the growth of tissue immediately after solidification Demonstrate.
  • the formation of equiaxed crystals is promoted, and more than 60% of the entire cross section can be made into a fine solidified structure (equiaxed crystals).
  • the Mg content is less than 0.0005% by mass, the amount of MgO and Z or MgO-containing oxides in the molten steel decreases, and the formation of solidified shells and the pinning action are reduced, so that the solidified structure cannot be made fine. .
  • the content of Mg exceeds 0.01% by mass, the effect of refining the solidified structure is saturated, so that a remarkable effect cannot be exhibited, and the cost of adding Mg or the like increases.
  • the electromagnetic stirrer 16 is disposed at a position 500 mm downstream from the molten metal surface (meniscus) 25 in the mold 13, and swirls along the inner wall of the mold 13 in the molten steel 11 in the mold 13. Apply a stirring flow.
  • the obtained piece has a very fine equiaxed crystal at the surface layer on which the stirring flow acts, and has a fine equiaxed solidification structure inside.
  • the fine equiaxed solidification structure improves the fluidity of the molten steel in the unsolidified portion 18b inside the piece, so that the occurrence of center porosity (Zak) and center deviation is suppressed.
  • the surface defects such as cracks and dents and the occurrence of internal defects can be eliminated in the piece, and also in the steel pipe manufactured from the piece.
  • light reduction may be applied to the piece. That is, the lower surface of the piece 18 is held by the support roll 22 using the rolling segment 19, and the upper central portion is pushed by about 3 to 10 mm by the convex portion 23 of the rolling port 24. Reduce the pressure so that By this light pressure reduction, the unsolidified portion 18b inside the piece 18 and the generated center porosity can be securely pressed.
  • the solid phase ratio is determined by driving a wedge into the piece, determining the state of erosion at the tip, and measuring the solidified (solid phase) and unsolidified areas of the piece.
  • This piece 18 does not need to perform a breakdown (large reduction) in which the reduction ratio exceeds 0.90, and can omit the rolling process performed by a rolling mill such as a general lumping process. Production costs can be greatly reduced.
  • the thus manufactured piece is cut into a predetermined length, reheated and formed by a pipe forming process, and then drilled with a plug to manufacture a seamless steel pipe.
  • the piece used in the production of this steel pipe has a fine solidified structure and, under light pressure, securely presses the center porosity, etc., so that when the inside is expanded with a plug and drilled, it is easy to use. It is possible to form a steel pipe of excellent quality by reliably preventing the inner surface from cracking and burrs.
  • the oxide contained in the surface layer of the piece is small.
  • the amount of oxides (oxides containing MgO) that elute when the surface comes into contact with acids, salt water, etc. can be reduced because the oxides present at and near the surface of the steel pipe drilled in the pipe process can be reduced. It is possible to suppress the corrosion of the steel pipe starting from this, thereby improving the corrosion resistance.
  • the present embodiment relates to fragment A of the present invention.
  • equiaxed crystals are within 3 times the average equiaxed crystal diameter. Internal: equiaxed crystals (60%)
  • Example 1 relates to a piece in which 60% of the solidified structure in the entire cross section in the thickness direction of the piece was made into an equiaxed crystal (equiaxed diameter of 1 to 5.2 mm) satisfying the following formula.
  • this piece some cracks were observed in the range of the columnar crystals in the surface layer, but the generation of internal defects such as internal defects such as cracks and Zaku ⁇ center segregation was suppressed. Good overall results (indicated by ⁇ ).
  • D is the diameter (mm) of the equiaxed crystal as a structure having the same crystal orientation
  • X is the distance (mm) from the surface of the piece.
  • the steel material rolled using this piece is good (shown by ⁇ ) with few occurrences of dents and cracks on the surface layer, and few internal defects such as cracks and Zaku ⁇ center segregation. Since the solidification structure is fine and micro-deflection is small, it is easy to be deformed in the direction of rolling down, and the toughness after processing is also good (indicated by ⁇ ) o
  • Example 2 relates to a piece in which the entire cross section in the thickness direction of the piece is made of an equiaxed crystal (equiaxed crystal diameter of 1.0 to 4.5 mm) satisfying the above formula.
  • equiaxed crystal equiaxed crystal diameter of 1.0 to 4.5 mm
  • the steel material rolled using this piece has very few occurrences of dents and cracks on the surface layer, and extremely few internal defects such as cracks and Zaku center segregation. It is.
  • this steel material has a fine solidification structure and small microsegregation, so that it can easily be deformed in the rolling direction and has excellent toughness after application (indicated by ⁇ ).
  • Example 3 the solidification structure in the entire cross section in the thickness direction of the piece was composed of equiaxed crystals (equiaxed diameters of 0.9 to 2.6) satisfying the above formula, and the maximum equiaxed crystal diameter was averaged. It relates to a piece whose size is less than three times the equiaxed crystal diameter. In this piece, the micro-folding formed on the surface layer is small, and the variation is suppressed, so that the occurrence of scabs and cracks is reduced. ⁇ ⁇ ⁇ No internal defects such as center segregation (indicated by ⁇ ).
  • the steel material rolled using this piece is extremely excellent in the surface defects such as scalp flaws and cracks on the surface layer, and internal defects such as cracks and Zac ⁇ center segregation (marked with ⁇ ). ), easily deformed in the direction of rolling down, and have excellent toughness after application (marked with ⁇ ).
  • the steel rolled using this steel piece has internal defects such as surface defects and cracks such as hedging flaws and cracks, and Zaku ⁇ center segregation (denoted by X).
  • the later evaluation of toughness etc. is also poor (indicated by X).
  • Comparative Example 2 relates to a piece in which the entire section in the thickness direction of the piece is equiaxed, but the equiaxed crystal of the surface layer (40% of the whole) does not satisfy the above formula.
  • surface defects such as scabs and cracks on the surface layer and internal defects such as center porosity and center segregation were investigated.
  • the evaluation was somewhat bad (indicated by ⁇ ).
  • the steel material rolled using this piece has slightly indented flaws and cracks on the surface layer, and slightly inferior internal defects such as Zaku center segregation (denoted by ⁇ ).
  • the later toughness is also slightly poor (indicated by ⁇ ).
  • the diameter D of the equiaxed (mm) is, D ⁇ 0. 08 X c 7 8 + 0. 5 (X: distance from the surface of ⁇ (mm) , D: when the diameter of the equiaxed crystal (mm) at the distance X from the surface of the piece is satisfied.
  • the piece was cut, and the solidification structure (in the state of equiaxed crystal diameter) of the cross section in the thickness direction and defects on the surface layer and inside of the piece were examined. Further, the slab was heated to 1250 ° C and then rolled, and defects and working characteristics on the surface layer and inside of the steel material were investigated. The results are shown in Table 3.
  • Example 1 60% or more of the solidified structure in the entire cross section of the piece was made into an equiaxed crystal (equiaxed crystal diameter of 1.5 to 3.2 mm) satisfying the above formula. And steel materials using the same. Regarding the quality of the pieces, cracks were relatively small, and internal defects such as cracks and Zaku center segregation were also good.
  • the quality of the steel rolled using this piece is good, with relatively few occurrences of dents and cracks on the surface layer, and few internal defects such as cracks and Zaku center segregation.
  • the toughness and the like are also good.
  • Example 2 relates to a piece in which the entire cross section of the piece was made into an equiaxed crystal (equiaxed crystal diameter of 0.3 to 2.9 mm) satisfying the above formula, and a steel material using the same. You. This piece has good quality with little occurrence of cracks and no internal defects such as cracks and Zaku ⁇ center segregation.
  • the quality of the steel material rolled using this piece is such that there are few occurrences of dents and cracks on the surface layer, and there are few internal defects such as cracks and zigzag center segregation. Etc. are also excellent.
  • Example 3 the entire cross section was occupied by equiaxed crystals having a diameter of 0.5 to 1.4 mm, and the maximum equiaxed crystal diameter was within 3 times the average equiaxed crystal diameter, and It relates to steel materials using the same.
  • ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ , ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ , ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ , ⁇ Zaku ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ has extremely excellent quality with less occurrence of cracks, no internal cracks, internal defects such as Zaku ⁇ center segregation.
  • the steel material rolled using this piece the occurrence of surface defects such as dents and cracks on the surface layer and the occurrence of internal defects such as cracks and Zac ⁇ center segregation are minimized. It also has excellent toughness after processing.
  • Comparative Example 1 columnar crystals were present in a range of 40% or more from the surface layer of the solidified structure in the section in the thickness direction of the piece, and the internal solidified structure was
  • the present invention relates to a piece having an equiaxed crystal diameter of 2.0 to 3.1 mm and a steel material using the same. In this piece and steel material, micro-deflection in the surface layer is large, cracks are generated during the construction and during the cooling process of the die, etc., and internal defects such as cracks and Zaku center segregation are also generated. .
  • Comparative Example 2 ⁇ pieces whose equiaxed crystal (equiaxed crystal diameter of 2.8 to 5.7 mm) and 40% of the solidification structure in the cross section in the thickness direction of the piece satisfies the above formula were used. It is related to the steel material that was used. In this piece and steel, cracks and the like in the surface layer could be considerably suppressed, but internal defects such as cracks and Zac ⁇ center segregation occurred inside.
  • the present embodiment relates to fragment B of the present invention.
  • the ⁇ piece is cut and the equiaxed crystal of the structure in the cross section in the thickness direction and the ⁇ piece are ground every 2 mm from the surface, and the crystal grain size of the surface at the same thickness position is measured.
  • ⁇ ⁇ Defects on the surface and inside of the piece were investigated. Furthermore, the surface piece and the surface flaw of the steel material rolled after heating the piece to 1250 ° C and the processing characteristics thereof were investigated. Table 4 shows the results. Show.
  • Example 1 shows that in Example 1, equiaxed crystals were formed in 30% of the entire cross-section in the thickness direction of the piece. It is related to the piece described in 2.7. This piece has no surface cracks or internal cracks (indicated by ⁇ ), and the steel material produced by rolling this piece has few surface defects and wrinkles (indicated by ⁇ ). Good processing characteristics (indicated by ⁇ ).
  • Example 2 is a piece shown by a solid line in FIG. 14 and has 60% or more equiaxed crystals formed therein, and the maximum crystal grain size / average crystal grain size is 1. It is related to the pieces of 7-2.5. This piece had no surface cracks or internal cracks (indicated by ⁇ ), and the steel material produced by rolling this piece had no surface flaws or cracks (indicated by ⁇ ). Very good processing characteristics (indicated by ⁇ ).
  • Comparative Example 1 is a piece indicated by a solid line in FIG. 15, in which the equiaxed crystal ratio inside the piece is as low as about 20%, the center is a coarse equiaxed crystal, and the same thickness position is obtained.
  • a part of the maximum grain size / average crystal grain size exceeded three times (2.5 to 4.7).
  • This chip has surface cracks and internal cracks (indicated by X), and the steel material produced by rolling this chip has surface flaws such as surface cracks and surface flaws (denoted by X). Display), processing characteristics are also poor (displayed with X).
  • Example 3
  • the present embodiment relates to fragment C of the present invention.
  • the piece was cut, and the equiaxed crystal ratio, the average equiaxed crystal diameter (mm), and the defects in the surface layer and inside of the solidified structure in the cross section in the thickness direction were examined. Further, the piece was heated to 1250 ° C and then rolled, and defects and working characteristics in the surface layer and inside of the steel material were investigated. Table 5 shows the results.
  • Example 1 shows that the number of inclusions contained in a piece of frit steel with a lattice mismatch of 6% or less with 5 ferrite was 104 Zcm 2 .
  • the size of the inclusions is 10 mm or more, the equiaxed crystal ratio is 62%, and the average equiaxed crystal diameter is 1.8 mm.
  • There are few surface defects such as flaws (indicated by ⁇ ), and internal defects such as internal defects such as cracks and Zaku ⁇ center segregation are also good (indicated by ⁇ ).
  • the steel rolled using this piece has few surface defects such as ringedge seam flaws (indicated by ⁇ ) and good internal defects such as cracks and Zaku ⁇ center segregation. (Indicated by ⁇ ), r-value, which is an index of workability, is also good (indicated by ⁇ ).
  • Example 2 the number of lattice mismatch is less than 6% of the inclusions of ⁇ 5 Fuwerai Bok contained in ⁇ the full Werai bets steel to 14 one Z cm 2, the size of the inclusions It is related to a piece whose diameter is equal to or less than 10 m, the equiaxed crystal ratio is 81%, and the average equiaxed crystal diameter is 1.3 mm. In this piece, there are few occurrences of surface defects such as cracks and dents (indicated by ⁇ ), and good internal defects such as internal defects such as cracks and Zaku ⁇ center segregation (indicated by ⁇ ) o
  • the steel material rolled using this piece has few surface defects such as ring edge seam flaws (indicated by ⁇ ) and good internal defects such as cracks and Zaku center segregation ( (Indicated by ⁇ ), r-value, etc., which are indicators of workability, are also good (indicated by ⁇ ).
  • Comparative Example 1 was a piece in which the number of inclusions contained in the piece was 70 Z cm 2 and the size of the inclusion was 10 m or less, and the equiaxed crystal ratio was 27%.
  • the average equiaxed crystal diameter is related to the piece of 2.5ii.
  • surface defects such as cracks and dents occur (indicated by X), and the inside of the piece has cracks, center porosity, center segregation, etc. A defect has occurred (indicated by X).
  • the steel material rolled using this piece has a scorch flaw on the surface layer, a ridged edge seam flaw, etc. (indicated by X), and has poor internal defects such as cracks, cavities, segregation ( (Indicated by X), r-value, which is an index of workability, is also poor (indicated by X).
  • Comparative Example 2 Among the metal compounds present per unit area of ⁇ number of 1 0 // m or less of the metal compounds, 45 Z cm 2 in the surface layer portion, the 45 Bruno cm 2 internally This is a piece in which the maximum equiaxed grain size in the surface layer and the maximum equiaxed grain size in the inside are large. These pieces also have internal defects such as cracks and dents, as well as internal defects such as cracks and Zaku segregation (indicated by X).
  • the steel material rolled using this piece has surface defects such as hedging and cracks, cracks, and internal defects such as Zaku center segregation (denoted by X), and is an index of workability.
  • the r value is also bad (indicated by X).
  • the present embodiment relates to fragment D of the present invention.
  • the piece was cut to examine the size of equiaxed crystals in the solidification structure in the cross section in the thickness direction and the defects in the surface layer and inside.
  • the piece was heated to 1250 ° C and then rolled, and the surface layer and inside of the steel material were examined for defects and working characteristics.
  • Table 6 Number of metal compounds (pieces / cm 2 ) Maximum equiaxed grain size (mm) Internal defects of rust or steel ⁇
  • Example 1 of the metal compound contained in ⁇ , 1 0 50 The number of m or less of the metal compound in the surface layer portion Z cm 2, to 66 / cm 2 inside, good, etc.
  • the present invention relates to a piece in which an axis crystal is formed. In this piece, there are few occurrences of cracks and dents, ridges and edge seam flaws, and few internal defects such as cracks and Zaku center segregation. In addition, the steel rolled using these pieces has less internal defects such as surface cracks, zigzag center segregation, etc. (indicated by ⁇ ). The r-value, which is an index of sex, is good (indicated by ⁇ ).
  • Example 2 Among the metal compounds present per unit area of ⁇ , 10 95 pieces m the number of the following metal compounds the surface layer portion Z cm 2, to 1 30 Z cm 2 inside, good This relates to a piece having an equiaxed crystal formed thereon. In this piece, the occurrence of cracks and dents, the occurrence of seam flaws, and the like are small, and the number of internal defects such as cracks and zigzag center segregation are also small. In addition, the steel material rolled using these pieces has few surface defects such as ridges and edge seam flaws, cracks, and internal defects such as zigzag center segregation (indicated by r). ⁇ ).
  • Comparative Example 1 of the metals compounds present per unit area of ⁇ , the number of the following metal compounds m, 45 pieces in the surface layer portion / cm 2, 46 pieces within Z cm 2
  • the present invention relates to a piece in which the maximum grain size and the maximum equiaxed grain size in the surface layer and the inside are large.
  • surface defects such as cracks and dents, and internal defects such as cracks and center segregation occur, and in the steel material rolled using this piece, Cracked surface defects and internal defects such as cracks and zigzag center segregation occur (indicated by X), and r values are poor (indicated by X).
  • Comparative Example 2 shows that metal present per unit area of a piece Among the compounds, the number of metal compounds of 10 m or less was 97 Zcm 2 at the surface layer and inside This relates to a piece having a size of 116 pieces / cm 2 and having a small equiaxed crystal grain size in the surface layer portion and the inside.
  • the occurrence of surface defects and internal defects is good (indicated by ⁇ ), but the r value is bad (indicated by X).
  • the present embodiment relates to a processing method I of the present invention.
  • the molten steel in the tundish does not contain Ca
  • the molten steel contains 0.0002%, 0.0005%, 0.0006%, and 0.0010% by mass of total Ca
  • 0.005% by mass of Mg is added to each molten steel. %, Then pouring into a mold with inner dimensions of 1200 mm in width and 250 mm in thickness to perform continuous production, and the chips are cooled by the mold and cooled by water spray from the supporting segment. After coagulation, the pressure was reduced by 3 to 7 dragons using a reduction segment, and then pulled out with a pinch roll.
  • Example 1 is a case without Ca in the molten steel, oxides and inclusions A 1 2 0 3 in the molten steel before Mg addition to the main component, and, in molten steel after Mg addition inclusions is the case for oxide was composed mainly of A1 2 0 3 ⁇ MgO and MgO.
  • the solidification structure of the piece obtained by manufacturing this molten steel is extremely fine, and the overall evaluation is extremely good (indicated by ⁇ ).
  • Example 2 is a case where the Ca in the molten steel to 0.0002 wt%, oxide inclusions in molten steel before Mg added pressure has the main component A 1 2 0 3, in the molten steel after Mg addition In the case where the inclusions are A 1 2 3 ⁇ MgO and oxides containing MgO as the main component It is. In this molten steel, no calcium-aluminate was generated, and the solidified structure of the piece obtained by producing the molten steel was extremely fine, and the overall evaluation was extremely good (indicated by ⁇ ).
  • Example 3 is a case where the Ca in the molten steel to 0.0005 wt%, oxide inclusions in molten steel before Mg added pressure has the main component A 1 2 0 3, the molten steel after Mg addition inclusions in is if the oxides in the main component of the a 1 2 0 3 ⁇ MgO and MgO.
  • this molten steel calcium'aluminate was not generated, and the solidified structure of the piece obtained by manufacturing the molten steel was extremely fine, and the overall evaluation was extremely good (indicated by ⁇ ).
  • Example 4 is a case where the Ca in the molten steel to 0.0006 mass%, inclusions in molten steel before Mg added pressure is another A1 2 0 3 of the main component, containing a few percent or less of CaO an oxide, also a case of oxide inclusions in the molten steel after Mg addition is composed mainly of A1 2 0 3 ⁇ MgO ⁇ CaO and MgO ⁇ CaO containing several% or less of CaO.
  • Example 5 is a case where the Ca in the molten steel to 0.0010 mass%, inclusions in molten steel before Mg added pressure is, other A 1 2 0 3 principal components, a few percent or less of CaO an oxide containing, also, inclusions in the molten steel after Mg addition, a 1 2 0 3 ⁇ MgO containing several% or less of CaO - is the case of oxides composed mainly of CaO and MgO ⁇ CaO .
  • Comparative Example 1 is a case where the Ca in the molten steel to 0.0012 mass%, inclusions in molten steel before Mg addition is A 1 2 0 3 - CaO (calcium aluminate Natick DOO ) and oxides in the main component of the inclusions in the molten steel after Mg addition, CaO- A1 2 0 3 - is the case of oxides in the main component of MgO.
  • the solidification structure of the piece obtained by forging this molten steel is coarse, and the overall evaluation is poor (indicated by X).
  • Comparative Example 2 is a case where the Ca in the molten steel to 0.015 mass%, rather inclusions force in the molten steel before Mg added pressure A1 2 0 3 - oxides of CaO (calcium aluminate Natick g) as a main component
  • the inclusions in the molten steel after the addition of Mg are oxides containing CaO-AI2O3-MgO as the main component.
  • the solidified structure of the piece obtained by manufacturing this molten steel was coarse, and the overall evaluation was poor (indicated by X).
  • Comparative Example 3 is a case where the Ca in the molten steel to 0.023 wt%, rather inclusions force in the molten steel before Mg added pressure A1 2 0 3 - in oxides of CaO (calcium Arumine g) as a main component There, inclusions in the molten steel after Mg addition, CaO - is the case of oxides in the main component of MgO - a 1 2 0 3.
  • the solidified structure of the piece obtained by manufacturing this molten steel was coarse, and the overall evaluation was poor (indicated by X).
  • the present embodiment relates to a processing method according to the present invention.
  • Example 1 is the case where 50 kg of A1 was added and deoxidation was performed, and then 0.75 kg of Mg was added. ⁇ The surface layer and the inside of the piece have no defects and the solidified structure is sufficiently fine, and the overall evaluation is good (indicated by ⁇ ).
  • Example 2 shows a case in which 75 kg of A1 was added, then 50 kg of an Fe-Ti alloy was added to perform deoxidation, and then 15 kg of Mg was added. ⁇ The surface layer and the inside of the piece have no defects, the solidified structure is sufficiently fine, and the overall evaluation is good (indicated by ⁇ ).
  • Example 3 shows a case where 50 kg of Fe—Ti alloy was added, 75 kg of A1 was added to perform deoxidation, and then 15 kg of Mg was added. ⁇ The surface and inside of the piece have no defects, the solidified structure is sufficiently fine, and the overall evaluation is good (indicated by ⁇ ).
  • Comparative Example 1 75 kg of A1 and 0.75 kg of Mg were simultaneously added to molten steel to perform deoxidation.
  • the surface structure of MgO-containing oxides the proportion of MgO is less than 10% (poor lattice matching degree between full Erai bets, coagulation
  • defects were generated on the surface layer and the inside of the piece, and the solidified structure became coarse as shown in Fig. 7, and the overall evaluation was poor (X Display).
  • Comparative Example 2 is a case where 50 kg of an Fe—Ti alloy was added, 15 kg of Mg was added, and then 75 kg of A1 was added to perform deoxidation.
  • oxides such as slag and deoxidation products contained in the molten steel and oxides generated when Mg is added to the molten steel are as follows:
  • the present invention relates to a treatment method in which a predetermined amount of Mg is added to molten steel so as to satisfy the expressions (1) and (2) (where k is mol% of oxide).
  • the molten steel was sampled, the composition of the oxide was measured by EPMA, and the added amount of Mg was adjusted so as to satisfy the above equations (1) and (2) to produce a composite oxide. Thereafter, the molten steel was continuously manufactured to produce pieces.
  • Mg-added caloric content Oxide composition (Mole oxide Fragment Fragment Fragment Steel material Item Overall evaluation
  • Example 1 shows that in Example 1, 125 kg of Mg was added to the molten steel, and the molten steel was stirred and the ⁇ value of the composite oxide contained in the molten steel (the left side of the above equation (1).
  • the index of the degree of lattice mismatch was set to 326, no internal defects occurred in the piece, the solidification structure was refined, the surface properties and workability of the steel material were good, and the overall evaluation was Good (indicated by ⁇ ) ⁇
  • Example 2 was a case in which 30 kg of Mg was added and the molten steel was stirred to set the ⁇ value of the composite oxide contained in the molten steel to 497, and defects were generated on the surface and inside of the piece. However, as shown in Fig. 9, the solidification structure is refined, the surface properties and workability of the steel are good, and the overall evaluation is good (indicated by ⁇ ).
  • Comparative Examples 1 and 2 were prepared by adding 85 kg and 30 kg of Mg and stirring the molten steel without considering the composition of the oxides contained in the molten steel before addition.
  • the ⁇ value of the composite oxide contained in the molten steel exceeded 500, internal defects were generated in the specimen, and in both cases, the solidification structure was coarsened and deteriorated as shown in Fig. 7, and the overall evaluation was Bad (indicated by X).
  • the present embodiment relates to a processing method according to the present invention.
  • Example 1 shows a case where the Ti concentration of molten steel having a Cr concentration of 0% was set to 0.013% by mass, the N concentration was set to 0.012% by mass, and then Mg was added by 0.0035% by mass. ⁇ Operation during manufacturing is stable, ⁇ has a fine solidified structure, and ⁇ has no defects in steel and steel. Overall evaluation is good (indicated by ⁇ ).
  • Example 2 shows a case where the Cr concentration of molten steel was set to 10% by mass, the Ti concentration was set to 0.020% by mass, the N concentration was set to 0.024% by mass, and then Mg was added to 0.0015% by mass. ⁇ Operation during manufacturing is stable, ⁇ has a fine solidified structure, and ⁇ has no defects in steel and steel. Overall evaluation is good (indicated by ⁇ ).
  • Example 3 shows a case where the Ti concentration in molten steel having a Cr concentration of 23% by mass was set to 0.125% by mass, the N concentration was set to 0.022% by mass, and then Mg was added by 0.0025% by mass. ⁇ Operation during production is stable, the solidification structure of ⁇ pieces is refined, and there are no defects in ⁇ pieces and steel materials, and the overall evaluation is good (indicated by ⁇ ).
  • the molten steel had a Cr concentration of 10% by mass, a Ti concentration of 0.021% by mass, a N concentration of 0.023% by mass, and no Mg was added. Operation becomes unstable due to clogging of nozzles during fabrication, and the solidification structure of the piece becomes coarse as shown in Fig. 7 and defects occur in the piece and steel, resulting in poor overall evaluation (X (Indicated by).
  • This embodiment relates to the processing method IV of the present invention.
  • the molten steel 150 tons in a ladle the thickness of slag covering the molten steel to lOOmiii, FeO, Fe 2 0 3 , MnO, and adjust the total mass of the S i 0 2 in a predetermined range, the The Mg alloy wire was supplied to the molten steel through the slag so that the molten steel had a pure Mg content of 50 kg (0.0333 mass).
  • the molten steel was formed at a forming speed of 0.6 mZ using a continuous forming apparatus having a thickness of 250 mm and a width of 1200 mm in a mold.
  • Example 1 is a case where the FeO in the slag before Mg addition, the total mass of Fe 2 0 3, MnO, Si0 2 to 2.5 wt%.
  • Mg in molten steel can be reduced to 0.0041 mass%, and Mg in flakes can be reduced to 0.0015 mass%, and the solidification structure of ⁇ flakes is refined.
  • Example 2 3 and 4, FeO in the slag before Mg addition, the total mass of Fe 2 0 3, Mn 0 and Si0 2, respectively, 11.3 wt%, 16.1 wt%, 22.4 It is the case where it was set to mass%.
  • Mg in molten steel is 0.0061% by mass, 0.0065% by mass, and 0.0063% by mass, respectively, and Mg in flakes is 0.0020% by mass, 0.0035% by mass, and 0.0031% by mass, respectively. ⁇
  • the solidification structure of the piece is also refined.
  • Example 5 FeO in the slag before Mg addition, Fe 2 0 3, nO, and a case where the total weight of Si0 2 to 28.5 wt%.
  • Mg in molten steel can be reduced to 0.0036% by mass, and Mg in flakes can be reduced to 0.0019% by mass. The solidified structure of flakes is refined.
  • Comparative Example 1 is a case where the FeO in the slag before Mg addition, Fe 2 0 3, Mn0, and Si0 2 of the total mass to 0.5% by weight.
  • Mg in molten steel is 0.0025% by mass
  • ⁇ Mg in flakes is 0.0009% by mass
  • the yield of Mg is poor.
  • ⁇ Part of the solidified structure of flakes is partially coarsened o
  • the present embodiment relates to the processing method V of the present invention.
  • a ladle receives 150 tons of molten steel, the thickness of the slag covering the molten steel is reduced, the CaO activity in the slag, the basicity of the slag is adjusted, and the Mg alloy wire is passed through the slag. Then, it was fed into molten steel and melted, and 50 kg of pure Mg was added to the molten steel.
  • the molten steel was formed at a forming speed of 0.6 mZ using a continuous forming apparatus having a thickness of 250 mm and a width of 1200 mm in a mold.
  • Example 1 is a case where the CaO activity in the slag was set to 0.2 and the basicity was set to 3, and the Mg alloy wire was added.
  • the Mg concentration in the molten steel after the Mg treatment was 0.0010% by mass, and the solidification structure of the piece could be refined (indicated by ⁇ ), and the overall evaluation was excellent (indicated by ⁇ ).
  • Example 2 and Example 3 are the cases where the CaO activity in the slag was 0.25 and 0.30, respectively, and the slag basicity was 7 and 10, respectively.
  • the Mg concentration in the molten steel is high, and the solidification structure of the ⁇ pieces is fine (indicated by ⁇ ), and the overall evaluation is excellent (indicated by ⁇ ).
  • Comparative Example 1 the CaO activity in the slag was set to 0.36, the basicity was set to 15, the Mg alloy wire was added, and the Mg in the molten steel after the Mg treatment was set to 0.0050% by mass. is there. ⁇
  • the solidification structure of the piece is coarse (indicated by X), and the overall evaluation is poor (indicated by X).
  • Comparative Example 2 is a case where the CaO activity in the slag was set to 0.42, the basicity of the slag was set to 20, and an Mg alloy wire was added, and the Mg in the molten steel after the Mg treatment was set to 0.0100% by mass. ⁇
  • the solidification structure of the piece is coarse (indicated by X), and the overall evaluation is poor (indicated by X).
  • the present embodiment relates to a continuous production method for producing pieces A to D of the present invention. Things.
  • 0.005% by mass of Mg was added to molten steel containing 16.5% by mass of chromium, and then a continuous forging was performed using a vibrating die with inner dimensions of 1,200mm in width and 250mm in thickness.
  • the ⁇ pieces were solidified by cooling with water and cooling by water sprinkling from the supporting segment, and pulled out with a pinch roll.
  • the embodiment is a case where an electromagnetic stirrer is installed so that the center of the core is located at a position of 500 mm downstream from the meniscus in the mold and the molten steel is stirred to form the core.
  • the number of MgO-containing oxides (inclusions) in the surface layer of the piece was reduced to reduce the solidification structure of the surface layer. It was made finer and defects such as surface cracks could be prevented.
  • the number of MgO-containing oxides (inclusions) increases inside the piece, and fine equiaxed crystals can be obtained. As a result, internal cracks can be eliminated and center segregation can be reduced. did it.
  • the steel material obtained by rolling the flakes has good corrosion resistance on the surface, and there is no occurrence of scratches or the like due to coarsening of the solidified structure.
  • Comparative Example 1 the molten steel was not stirred by the electromagnetic stirring device. Mg The number of oxides (inclusions) containing MgO increased in the surface layer and inside of the piece, and the solidification structure in the surface layer and inside could be refined, but the MgO-containing oxide originated on the surface of the rolled steel. Corrosion spots were found to be present. This steel material is bad for practical use.
  • Comparative Example 2 is a case in which molten steel was stirred by an electromagnetic stirring device without adding Mg. ⁇ The solidification structure inside the piece became coarse, internal cracks and center deviation occurred, and the steel material produced by processing this piece produced scratches and the like due to the coarsening of the solidification structure. .
  • the present embodiment relates to the application of the above-described continuous structure of the present invention to the structure of ferritic stainless steel, and to the manufacture of a seamless steel pipe from the manufactured piece. .
  • 0.0010% by mass of Mg was added to molten steel containing 13.0% by mass of chromium, and then a continuous forging was performed using a vibrating mold having an inner dimension of 600 mm in width and 250 mm in thickness.
  • the ⁇ pieces were solidified by cooling by the mold ⁇ and cooling by sprinkling water from the support segment, and the pieces were pulled out by pinch rolls.
  • Table 14 shows the results.
  • Table 14 Magnetic stirring conditions for molten steel Light pressure conditions ⁇ Port of piece of steel pipe Item g Mg addition amount Solidification Inner / Surface
  • Example 1 is a case where 0.0010% by mass of Mg was added to molten steel to produce a seamless steel pipe. ⁇
  • the solidification structure of the piece is finer (indicated by ⁇ ), and the surface and inside of the steel pipe when drilled have no cracks or dents (indicated by ⁇ ), and the overall evaluation is good (indicated by ⁇ ) ).
  • Example 2 an electromagnetic stirrer was installed so that the center of the core was located at a position 500 minutes downstream from the meniscus in the mold and the molten steel was stirred, and the structure was stirred from the position where the solid fraction became 0.5. This is the case where light reduction is started.
  • Mg The number of MgO-containing oxides in the surface layer of the piece is reduced, ⁇
  • the solidified structure of the entire piece can be refined (indicated by ⁇ ), and no cracks or dents are found on the surface and inside of the steel pipe when drilled. None (indicated by ⁇ ), the overall evaluation was excellent (indicated by ⁇ ).
  • Example 3 the molten steel was manufactured by adding 0.0010% by mass of Mg, and the range from the position where the solid phase ratio became 0.4 to solidification was lightly reduced at a total indentation depth of 7 mm. This is the case. ⁇
  • the solidification structure of the piece can be refined (indicated by ⁇ ), the surface and inside of the steel pipe when drilled are free of cracks and dents (indicated by ⁇ ), and the overall evaluation is excellent (indicated by ⁇ ) Things.
  • Comparative Example 1 was a case where the molten steel was manufactured without adding Mg, and was subjected to electromagnetic stirring at a position 500 downstream from the meniscus to bore holes. ⁇ The solidification structure of the piece becomes coarse (indicated by X), and when drilled, cracks and dents occur on the surface and inside of the steel pipe (indicated by X), and the overall evaluation is poor (indicated by X) )
  • Comparative Example 2 is a case in which the molten steel was manufactured without adding Mg, and the range from the position where the solid phase ratio was 0.4 to solidification was lightly reduced with a full indentation depth of 7 thighs. ⁇ The solidification structure of the piece becomes coarse (indicated by X), and cracks and dents occur on the surface and inside of the drilled steel pipe (indicated by X), and the overall evaluation is poor (indicated by X) ) Industrial applicability
  • the piece of the present invention has surface defects such as cracks and dents generated in the piece due to distortion and stress in the solidification process, surface defects caused by inclusions, etc., internal cracks, center porosity (Zaku), and center segregation.
  • surface defects such as cracks and dents generated in the piece due to distortion and stress in the solidification process, surface defects caused by inclusions, etc., internal cracks, center porosity (Zaku), and center segregation.
  • the occurrence of internal defects such as is suppressed.
  • the chip of the present invention is excellent in processing characteristics and quality characteristics, further, does not require the care of the chip such as grinding and the like, and reduces the generation of waste as much as possible. It is expensive.
  • the treatment method of the present invention adjusts the characteristics of the molten steel and the form of inclusions in the molten steel so that the solidified structure is refined during the solidification of the molten steel. This is an extremely useful method for treating molten steel.
  • the continuous manufacturing method for producing a piece of the present invention further enhances the function and effect imparted to molten steel by the processing method of the present invention during continuous manufacturing.
  • the steel material such as a steel sheet and a steel pipe manufactured by processing the piece of the present invention has, as in the case of the piece, the occurrence of surface defects and internal defects suppressed, and the processing characteristics and the quality characteristics are also reduced. It will be excellent.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Continuous Casting (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

L'invention concerne une pièce en acier moulé présentant d'excellentes aptitudes au formage, se caractérisant en ce que 60 % ou plus de la section transversale est constituée de grains équiaxiaux, selon la formule D < 1,2 X1/3 + 0,75, dans laquelle D représente un diamètre (mm) d'un grain équiaxial dont la structure présente la même orientation que le cristal et X représente la distance par rapport à la surface (mm) de la pièce d'acier moulé. La pièce en acier moulé et le produit en acier produit par le formage de la pièce en acier moulé présentent une surface extrêmement réduite et d'infimes défauts internes.
PCT/JP2000/002296 1999-04-08 2000-04-07 Piece en acier moule et produit en acier presentant une excellente aptitude au formage et procede de traitement d'acier en fusion prevu a cet effet, et procede de production associe WO2000061322A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
AU36746/00A AU753777B2 (en) 1999-04-08 2000-04-07 Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof
US09/719,206 US6585799B1 (en) 1999-04-08 2000-04-07 Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof
CA002334352A CA2334352C (fr) 1999-04-08 2000-04-07 Piece en acier moule et produit en acier presentant une excellente maniabilite, procede de traitement d'acier en fusion et procede de fabrication d'acier en fusion et de materiau en acier
EP00915437A EP1099498A4 (fr) 1999-04-08 2000-04-07 Piece en acier moule et produit en acier presentant une excellente aptitude au formage et procede de traitement d'acier en fusion prevu a cet effet, et procede de production associe
US10/222,362 US6918969B2 (en) 1999-04-08 2002-08-16 Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material

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JP11/101163 1999-04-08
JP11101163A JP2000288698A (ja) 1999-04-08 1999-04-08 圧延加工特性に優れた鋳片及びそれを用いた鋼材
JP10237999A JP2000288693A (ja) 1999-04-09 1999-04-09 品質特性に優れた鋳片及びそれを用いた鋼材
JP11/102184 1999-04-09
JP11102184A JP2000288692A (ja) 1999-04-09 1999-04-09 連続鋳造により製造した鋳片及びそれを用いた鋼材
JP11/102379 1999-04-09
JP11367399A JP2000301306A (ja) 1999-04-21 1999-04-21 品質と加工特性に優れた鋳片及びそれを加工した鋼材
JP11/113673 1999-04-21
JP11/133223 1999-05-13
JP11133223A JP2000328173A (ja) 1999-05-13 1999-05-13 加工特性に優れた鋳片及びそれを加工した鋼材
JP11/146443 1999-05-26
JP11146443A JP2000334559A (ja) 1999-05-26 1999-05-26 品質に優れた鋼の連続鋳造方法
JP14685099 1999-05-26
JP11/146850 1999-05-26
JP11/180112 1999-06-25
JP18011299A JP4279947B2 (ja) 1999-06-25 1999-06-25 溶鋼のＭｇ処理方法
JP11237031A JP2001058242A (ja) 1999-08-24 1999-08-24 クロム含有溶鋼の鋳造方法及びそれを用いたシームレス鋼管
JP11/237031 1999-08-24
JP26727799A JP2001089807A (ja) 1999-09-21 1999-09-21 溶鋼の処理方法
JP11/267277 1999-09-21
JP2000/22056 2000-01-31
JP2000022056 2000-01-31
JP2000/66137 2000-03-10
JP2000066137A JP2001252747A (ja) 2000-03-10 2000-03-10 品質特性に優れた溶鋼の処理方法
JP2000/86215 2000-03-27
JP2000086215A JP4287974B2 (ja) 2000-03-27 2000-03-27 微細凝固組織特性を有する溶鋼の処理方法

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US10/222,362 Division US6918969B2 (en) 1999-04-08 2002-08-16 Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material

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KR20200116991A (ko) * 2018-03-30 2020-10-13 닛테츠 스테인레스 가부시키가이샤 내리징성이 우수한 페라이트계 스테인리스강
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EP2308617A2 (fr) 2011-04-13
EP1099498A4 (fr) 2004-10-27
EP2308616B1 (fr) 2016-01-06
EP2292352B1 (fr) 2014-05-14
EP2292352A1 (fr) 2011-03-09
EP2308617A3 (fr) 2011-08-10
AU753777B2 (en) 2002-10-31
KR20050103249A (ko) 2005-10-27
AU3674600A (en) 2000-11-14
KR100550678B1 (ko) 2006-02-09
KR100706973B1 (ko) 2007-04-13
CN1321766C (zh) 2007-06-20
US20030015260A1 (en) 2003-01-23
CN1631578A (zh) 2005-06-29
EP2308617B1 (fr) 2018-02-21
US6585799B1 (en) 2003-07-01
CA2334352C (fr) 2005-11-15
US6918969B2 (en) 2005-07-19
EP1803512A2 (fr) 2007-07-04
KR20010025119A (ko) 2001-03-26
EP2308616A1 (fr) 2011-04-13
CA2334352A1 (fr) 2000-10-19
EP1099498A1 (fr) 2001-05-16
EP1803512B1 (fr) 2014-05-14
EP1803512A3 (fr) 2007-10-31

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